bluuebunny/crossref_metadata_2025 huggingface dataset:
Applications of Surface Analysis by Laser Ionization (Sali) to Insulators and II–VI Compounds
Authors: Becker C. H. , Stahle C. M. , Thomson D. J.
Published: March 2011

Examples of the mass spectrometry of sputtered or evaporating neutral species obtained by SALI are presented for NBS Glass 610 (primarily a silicate), and an anodic oxide of HgCdTe. For the NBS glass, a SIMS spectra was recorded for comparison with SALI using the same apparatus. The raw SALI spectra of the glass is in semiquantitative accord with the known composition, in contrast to SIMS. Relative secondary ion yields can be determined for unknown complex materials by comparing SALI and SIMS spectra. Depth profiling measurements on the anodic oxides of Hg1−xCdxTe show a significant though depleted concentration of Hg in the oxide in contrast to numerous other analyses; this result is corroborated by RBS studies. Hg and also Te evaporation is monitored in real-time by SALI with large dynamic range capabilities.
High Temperature Raman Studies of Phase Transitions in Thin Film Dielectrics
Authors: Exarhos Gregory J.
Published: March 2011

Rapid and unambiguous characterization of crystalline phases in submicron sputter deposited TiO2 films on silica substrates can be inferred from measured Raman spictra. Pure anatase and rutile, mixed phase, and amorphous films to thicknesses of several hundred Angstroms and greater yield Raman spectra exhibiting little interference from the substrate when the appropriate component of the scattered light is analyzed. In situ Raman spectra were acquired as a function of temperature to 900°C using conventional radiant heating techniques and to temperatures near 2000°C using 10.6μ radiation from a CW CO2 laser as a localized heating source. Pulsed Raman excitation/gated deiection techniques were used to minimize blackbody radiation interference at these high temperatures. Anatase and amorphous TiO2 films transform irreversibly to the rutile phase at temperatures below 900°C while rutile appears to be stable at much higher temperatures. Measurements performed on uncoated silica substrates at temperatures where the glass becomes fluid suggest that the strongly crosslinked glass has partially transformed into a chain-like structure.
Atomic Interactions in Silicon-Metal Complexes on W(110)
Authors: Wrigley John D. , Ehrlich Gert
Published: March 2011

With the field-ion microscope one not only can locate individual atoms at a surface, but under some circumstances also can discriminate between chemically different species. These capabilities are illustrated in an examination of the strength of binding in silicon-metal surface clusters and in a detailed analysis of their mobility.
The Thickness Effect on the Microstructure of Sputtered Films Studied by a New X-Ray Diffraction Method
Authors: Hecq M.
Published: March 2011

The microstructure of sputtered platinum thin films has been investigated by X-ray diffraction analysis. The (111) reflection was analysed by the variance and the Fourier methods. The effective particle size was calculated from the variance slope coefficient and the microstrain from the Fourier cosine coefficients assuming that the effective sizes calculated from both methods are identical. Various thickness thin films have been studied. The effective particle size (Dev) increases with ev increasing film thickness until a thickness of ≈ 1500 Å, then Dev becomes constant and independent on the thickness. The microstrain varies in an inverse way to Dev ; it decreases with increasing thickness. Above a thickness of 1500 Å, the microstrain is constant.
TEM/STEM Sample Preparation for the Investigation of Solid State Structures: Applications to Electronic Devices and Computer Components
Authors: Flutie Richard E.
Published: March 2011

There has been a resurgence of the TEM/STEM being applied to the inspection and microanalysis of solid state electronic structures and devices. As the IC industry scaled down to submicron lines and spaces the IC designer, manufacturing processor and failure analyst required better “eyes” than the SEM could give. In addition to the image improvement, the TEM/STEM provided the microanalysis capability of microelectron diffraction (<30 angstroms) and sub-micron EDXA of ultra-thinned samples.
High Resolution Microanalysis of Interfaces
Authors: Garratt-Reed Anthony J.
Published: March 2011

Of great importance in many fields of endeavor is the analysis of solutes segreoated to grain boundaries in solids. Such segregation is usually (but not always) limited to the boundary plane, and can, therefore, be thought of as being “two-dimensional”.
Convergent-Beam Diffraction in the Characterization of Crystalline Phases
Authors: Eades J. A. , Kaufman M. J. , Fraser H. L.
Published: March 2011

Convergent-beam diffraction in the transmission electron microscope is a powerful technique for the characterization of crystalline materials. Examples are presented to show the way in which convergent-beam zone-axis patterns can be used to determine: the unit cell; the symmetry; the strain of a crystal. The patterns are also recognizable and so can be used, like fingerprints, to identify phases.
Cold Alchemi: Impurity Atom Site Location and the Temperature Dependance of Dechannelling
Authors: Spence J. C. H. , Graham R. J. , Shindo D.
Published: March 2011

Recent applications of the “Atom Location by Channelling Enhanced Microanalysis” (ALCHEMI) are summarised. This is a quantitative method for determining the sites of impurity atoms in crystals using an electron microscope and X-ray analysis system. Since the fractional site occupancies are given in terms of measured X-ray counts alone, it involves no adjustable parameters. New experiments have been performed on the temperature dependence of characteristic X-ray production under channelling conditions for InP and GaAs. We conclude that low temperatures will give more accurate results for “ALCHEMI” in some materials due to the reduction in diffuse inelastic phonon scattering, and that the study of this temperature dependence may provide new information from small areas or particles on the correlations amongst atom motions due to thermal vibration.
Role of the Critical Voltage Effect in Materials Characterization
Authors: Fisher Robert M.
Published: March 2011

The HVEM “critical voltage” effect can provide quantitative information about intrinsic crystal parameters that cannot be obtained easily on a microscopic scale by other techniques. For pure elements, more accurate atomic scattering amplitudes and Debye temperatures have been determined. In binary alloys, the occurrence of segregation, short or long range order or clustering can be evaluated and charge distribution or transfer and atomic bonding changes detected in favorable cases.
Diffusion Measurements by Analytical Electron Microscopy
Authors: Romig A. D.
Published: March 2011

The analytical electron microscope (AEM) has been used to measure the concentration gradients which form in single and multiphase diffusion couples. The procedures used to collect x-ray microanalytical data and reduce that data to elemental compositions are typical of those used to quantify x-ray data generated in thin films. The primary difficulty in analyzing diffusion couples with the AEM is sample preparation. The principle advantage of the AEM as a tool to measure diffusion induced concentration gradients is its high spatial resolution, approximately 20 to 100 times better than that of the electron microprobe which has been traditionally used to measure these concentration profiles. As a consequence, the AEM data can yield diffusivities as much as 5 orders of magnitude smaller than those obtained from electron microprobe data. This paper will review the fundamental principles of the determination of diffusion coefficients from the concentration gradients measured in single and multiphase diffusion couples and the basic considerations of thin foil x-ray microanalysis. With this understanding of the basic concepts, recent studies of diffusion in Ta-W and U-Nb will be discussed.
AEM Microanalysis of Phase Equilibria in Ni3Al Intermetallic Alloys Containing Iron
Authors: Bramfitt Bruce L. , Michael Joseph R.
Published: March 2011

In order to fully exploit the potential of Ni3Al alloys containing iron, it is necessary to characterize the phase relationships at the Ni-rich region of the Ni-Al-Fe ternary phase diagram. Due to the fine scale structures observed, a technique with high spatial resolution is required. X-ray microanalysis in the analytical electron microscope (AEM) provides a sufficiently high spatial resolution to determine the composition of the various phases occurring in this system. In this study, the isothermal section at 1000°C was evaluated in a series of alloys having nickel contents greater than 65 wt%. In Ni3Al, Fe can substitute for either Ni or Al in the ordered face-centered cubic lattice having an Ll2 structure. However, in substituting Fe for Ni one finds that the solubility limit is quickly exceeded at about 5 wt% Fe with the resultant formation of a ordered body-centered cubic (B2) phase at high temperature, which transforms martensitically upon quenching. Also, in substituting Fe for Al, the solubility limit is exceeded at about 5 wt% Fe with the formation of a disordered, face-centered cubic Ni-rich terminal solid solution. Thus, a very narrow range of alloy compositions exist where Fe can substitute for Ni and Al and preserve a single-phase L12 structure. It was found that the maximum solubility of Fe in Ni3Al at 1000°C was 17.3 wtpercnt; at 70.3 wt% Ni and 12.4 wt% Al.
High Resolution Moire Imaging of Small Precipitates
Authors: Kesternich W.
Published: March 2011

Small precipitates of high lattice mismatch with respect to the matrix may be investigated by high resolution and high contrast moiré fringe images in TEM. One group of such precipitates are the MX-type precipitates with M = Ti, V, Zr, Nb, Hf, Ta, and X = C,N that form in austenitic steels. The usefulness of moiré images for the investigation of these MX-type precipitates is demonstrated and compared to other electron imaging and diffraction methods. The moiré technique has been used to study (a) nucleation and growth of precipitates, (b) the evolution of dual precipitate structures at grain boundaries, (c) morphology and faceting of small precipitates (∼10 nm diameter), (d) lattice parameter differences due to variation in precipitate chemical composition, (e) interaction of precipitates with dislocations, (f) gas atom trapping at precipitates, and (g) irradiation induced precipitate nucleation at point defect clusters.
TEM Studies of Precipitate Growth at the Atomic Level
Authors: Howe J. M. , Gronsky R.
Published: March 2011

Recent advances in transmission electron microscopy instrumentation and technique now make it possible to study the shape-evolution of precipitates in metallic alloys at the atomic level. This investigation demostrates how a combination of transmission electron microscopy techniques; namely, high-resolution electron microscopy, image simulation, energy-dispersive x-ray spectroscopy and convergent-beam electron diffraction are used to characterize the atomic structures, chemistry and growth mechanisms of γ' precipitate plates in an Al-4.2 a/o Ag alloy aged for 30 min. at 350°C. The complimentary information obtained from each of these techniques allows modelling of the growth process at the atomic level, thus providing insight into the basic precipitation behavior of alloys.
A Quasicrystalline Decagonal Phase in Al-Fe-Ce
Authors: Angers L. H. , Marks L. D. , Weertman J. R. , Fine M. E.
Published: March 2011

A number of dispersed phases in Al-Fe-Ce alloys, varying structurally and chemically, have been observed by TEM. Of particular interest were rod-like particles which showed five-fold symmetry and irrational spacings. These dispersoids contain linear features, a periodic, columnar structure parallel to the five-fold axis, aperiodic spacings perpendicular to the five-fold axis and were coherent in one direction with the Al matrix. The evidence indicates a two-dimensional Penrose tiling with a columnar structure, possibly a stacking of eclipsed pentagonal units.
Quantitative Microanalysis of Fine Precipitates in Microalloyed Steels
Authors: Michael Joseph R.
Published: March 2011

Matrix and grain boundary precipitation in austenite has been studied in two Nb/V microalloyed steels with different V levels, which were given a number of different heat treatments after hot deformation. The steel with a higher V level was found to have a greater number of fine carbonitride precipitates in the matrix. In both steels, the precipitates became more Nb-rich as the aging temperature was increased from 854°C to 1066°C. For a given steel and heat treatment, the matrix precipitates were generally more Nb-rich than the grain boundary precipitates.
Electron Microscopy Observations of Precipitation During Tempering of Vasco X-2M Steel and its Relation to Impact Toughness
Authors: Krzanowski James E.
Published: March 2011

Vasco X-2M is a low carbon tool steel which is being considered for critical gear applications. Since toughness is an important property for these applications, the Charpy V-notch impact energy was tested as a function of tempering temperature and found to drop considerably at 480C temper and above. A TEM investigation was carried out in order to better understand the results of this test. The precipitation sequence of carbides was examined along with their morphology, structure and orientation relation to the matrix. The precipitation of the intralath M3C carbides occurred on quenching from austenite. These carbides were then present in all tempered samples. M2C carbides were observed at 480C and 590C temper, and evidence for precipitation of these carbides was based on hardness data at 480C temper and TEM observations at 590C temper. After aging 200h at 590C, the ceitientite was observed to be in the process of transforming in an in-situ manner to an M7C3 carbide. The minimum in the Charpy impact energy was found to occur when both coarse M3C and a very fine dispersion of M2C were present in the microstructure.
Crystalline-to-Amorphous Transitions in Ti-Ni Alloys
Authors: Pelton R. , Moine P. , Noack M. A. , Sinclair R.
Published: March 2011

Ti-Ni alloys have been made amorphous over a broad composition range by sputter deposition, ion implantation and electron irradiation. Structural analysis of these alloys was made by electron diffraction techniques. Microdensitometer traces of diffraction patterns produced scattering profiles from which radial distribution functions (RDF's) were derived. The results from this analysis were comparable to those from x-ray diffraction studies on similar alloys. It was found that the positions of the intensity maxima vary systematically with alloy composition. However, values of coordination number were less precise due to experimental uncertainties. Furthermore, no dramatic differences were observed in the RDF's of the samples amorphized by the three techniques.
In-Situ High Resolution Transmission Electron Microscopy of Dynamic Events During the Amorphous to Crystalline Phase Transformation in Silicon
Authors: Parker M. A. , Sigmon T. W. , Sinclair R.
Published: March 2011

A technique has been developed which employs high resolution transmission electron microscopy (HRTEM) for the observation of the atomic mechanisms associated with solid state phase transformation as they occur at elevated temperatures. It consists of the annealing in-situ of cross-section transmission electron microscopy (TEM) specimens that have been favorably oriented for lattice fringe imaging and the video-recording of dynamic events as they occur in real-time. By means of this technique, we report the first video-recorded lattice images of crystallographic defect motion in silicon, viz. the motion of dislocations and stacking faults, as well as the first such images of the atomic mechanisms responsible for the amorphous to crystalline (a-c) phase transformation, viz. heterogeneous nucleation of crystal nuclei, coalescence of crystal nuclei by co-operative atomic processes, ledge motion at the growth interface, and normal growth in silicon. This technique holds great potential for the elucidation of the atomic mechanisms involved in reaction kinetics in the solid state.
Application of Hrem in Studying Amorphisation of Intermetallic Compounds
Authors: Luzzi D. E. , Mori H. , Fujita H. , Meshii M.
Published: March 2011

Electron irradiation induces many intermetallic compounds to become amorphous. As this irradiation is capable of producing only isolatedpoint defects for each collision event, an understanding of this amorphisation proqess has a special significance with respect to the understanding of amorphous materials. This paper will report the results of HREM observations of an intermetallic compound in the Cu-Ti alloy system. High resolution micrographs will be presented to demonstrate that the energy associated with the irradiation induced chemical disordering is the major driving force in the amorphisation process. Also, the utility of the HREM in the study of amorphisation and the amorphous structure will be discussed.
High Spatial Resolution Microanalysis of Catalyst Particles
Authors: Lyman C. E.
Published: March 2011

Qualitative and quantitative analysis of small catalyst particles is possible in the analytical electron microscope down to analysis areas on the order of 10 nm in diameter. The location of elements in the image field can be determined either by placing the electron probe on a particu-lar image feature or by forming a digital x-ray image showing the distribu-tion of various elements. In either case analysis of specimens of well defined thickness such as microtomed thin sections preserves spatial relationships in catalyst particles and simplifies interpretation of single element x-ray images. Electron energy loss spectroscopy can be combined with x-ray spectroscopy to reduce the ambiguity in x-ray spectra caused by spurious x-rays generated by electrons scattered from the analy-sis area to regions of high concentrations of elements removed from the analysis area.
The Local Atomic Arrangement in Amorphous Sixc1−x:H By Electron Energy Loss Spectroscopy and Electron Diffraction
Authors: Tafto J. , Kampas F. J.
Published: March 2011

We have used electron energy loss spectroscopy (EELS) and electron diffraction to study the local atomic arrangement in amorphous SixC1−x:H in the composition range 0.37 < × < 1. In the thin films, which were pre-pared by radio-frequency glow discharge from a mixture of methane and sil-ane, the π at the K-edge of C does not show up even for the highest C-content, i.e., Si0.37C0.63, consistent with fourfold coordinated C in the whole composition range studied. Also the electron diffraction results suggest a tetrahedral network. Models where the minority element is sur-rounded by four atoms of the majority element, fit the experimental data better than models based on a random distribution of Si and C on the tetra-hedral network.
Grain-Boundary, Glassy-Phase Identification and Possible Artifacts
Authors: Simpson Y. Kouh , Carter C. B. , Sklad P. , Bentley J.
Published: March 2011

Specimen artifacts such as grain boundary grooving, surface damage of the specimen, and Si contamination are shown experimentally to arise from the ion milling used in the preparation of transmission electron microscopy specimens. These artifacts in polycrystalline, ceramic specimens can cause clean grain boundaries to appear to contain a glassy phase when the dark-field diffuse scattering technique, the Fresnel fringe technique, and analytical electron microscopy (energy dispersive spectroscopy) are used to identify glassy phases at a grain boundary. The ambiguity in interpereting each of these techniques due to the ion milling artifacts will be discussed from a theoretical view point and compared to experimental results obtained for alumina.
Microstructural Changes in Deformed Silicon Nitride and Silicon Carbide
Authors: Tighe Nancy J.
Published: March 2011

The microstructural changes that are associated with creep in silicon nitride and silicon carbide are described and related to the creep mechanisms. Creep in hot-pressed silicon nitride and sintered silicon carbide involves mechanisms of cavitation and crack propagation within the bonding phase when the temperatures are below those necessary to activate plastic deformation within the matrix grains. In hot-pressed, magnesia doped silicon nitride the bonding phase is amorphous magnesium silicate and the creep damage involves decohesion and sliding of the matrix grains within the soft bonding phase. In yttria-doped silicon nitride the bonding phase is crystalline and diffusional interactions between this phase, the matrix and the atmosphere dominate the creep process. A similar condition is found in siliconized silicon carbide whereby the creep is controlled by the behavior of the silicon phase.
TEM and SEM Studies of MOCVD-Grown GaP on Si
Authors: Ai-Jassim M. M. , Olson J. M. , Jones K. M.
Published: March 2011

GaP and GaP/GaAsP epitaxial layers have been grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). These layers were characterized by SEM and TEM plan-view and cross-sectional examination. At growth temperatures ranging from 600° C to 800° C, the initial stages of growth were dominated by three-dimensional nucleation. TEM studies showed that at high temperatures the nuclei were generally misoriented with respect to each other yielding, upon coalescence, polycrystalline layers. The growth of single-crystal layers was achieved by nucleating a 30–50 nm layer of GaP at 500° C, followed by annealing and continued growth at 750 ° C. The defect density in these structures was investigated as a function of various growth parameters and substrate conditions. A high density of structural defects was generated at the Si/GaP interface. The use of 2° off (100) Si substrates resulted in GaP layers free of antiphase domains. These results and their implications are discussed.
The Potential of High-Resolution Transmission Electron Microscopy for Imaging Impurities at Dislocations and Grain Boundaries in Silicon
Authors: Rose Jamie H. , Gronsky R.
Published: March 2011

The application of HRTEM to the study of equilibrium segregation in linear and planar silicon defects is evaluated with image calculations. For this purpose, models for interstitial segregation in the Σ=9 grain boundary and donor segregation in the 30° partial dislocation are proposed. These models possess columns of impurity atoms.

Systematic image simulations were first examined for an impurity column in an otherwise perfect <110> silicon crystal. Optimum contrast and exposure times require samples of thickness equal to the transmitted beam extinction distance. Arsenic and boron are detectable with a column concentration of about 5%. With diffuse phase contrast imaging, this limit is roughly halved.

The above imaging conditions may be used to distinguish different defect core models.

Observation of segregated impurities requires somewhat higher concentrations in addition to image comparisons with a clean defect. Quantitative analysis necessitates careful image simulation comparisons and improvements in knowledge of microscope parameters.
Electron Diffraction Study of Multilayer Structures with Partially Coherent Illumination
Authors: Otsuka N. , Choi C. , Kolodziejski L. A. , Gunshor R. L.
Published: March 2011

The effect of partial coherency on electron diffraction patterns of Cd1−xMnxTe – Cd1−yMny Te superlattices has been investigated. Observed diffraction patterns are compared with intensity calculations performed using dynamical diffraction theory with a model of an extended incoherent monochromatic source. From this study, a new method of electron diffraction for characterization of multilayer structures can be developed. Under the condition that the lateral coherent distance of the incident beam covers two adjacent layers, diffraction beams arising from the two layers give rise to an interference fringe in a diffraction spot. With this type of diffraction pattern, one can determine the refractive index of a crystal in the multilayer structure.
Application of Analytical Electron Microscopy to Ion Implantation and Near Surface Microstructures
Authors: Sklad P. S.
Published: March 2011

Surface modification using ion beam techniques is recognized as an important method for improving surface controlled properties of metallic, ceramic, and semiconductor materials. Determination of the microstructure and composition in regions located within a few hundred nanometers of the surface is essential to gaining an understanding of the mechanisms responsible for the improved properties. Analytical electron microscopy (AEM), high resolution microscopy, and microdiffraction are ideally suited for this purpose. These techniques are powerful tools for characterizing microstructure in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer and annealing behavior. Such analyses allow correlations with theoretical models, property measurements and results of complementary techniques. The proximity of the regions of interest to the surface also places stringent requirements on specimen preparation techniques. The power of AEM in examining the effects of ion implantation will be illustrated by reviewing the results of several investigations. A brief discussion of some important aspects of specimen preparation will also be included.
Microcomputers in Teching Materials Science and Engineering: TK! Solver Models
Authors: Brostow Witold , Turner David P.
Published: March 2011

This work is a part of a larger program, aimed at improving teaching of materials science and engineering (MSE) and also at better communication between teachers and learners. Since every incoming Drexel University student is provided with a microcomputer, the objective of this project was to develop learning tools for MSE usable with a microcomputer.

We have used TK! Solver, a meta-expert system, capable among other things to solve overdetermined systems of simultaneous equations. In distinction to standard programming, interchanging the roles between unknown and known parameters does not require program changes. Various operations which ordinarily would involve attaching subroutines from a libraryare accomplished by simple choices from menus. We have developed a large number of TK! Solver models for MSE, covering various materials properties (mechanical, thermophysical, electrical…), as well as all important classes of materials.
Materials Education and the National Laboratories
Authors: Hecker Siegfried S.
Published: March 2011

The U.S. Department of Energy is one of the principal government sponsors of materials R&D, both at universities and at the DOE National Laboratories. The National Laboratories are a major employer of graduates with materials education. I will discuss some of the Laboratories' specific needs as well as some of the special opportunities offered at the laboratories for materials education.
Recruitment and Retention of Lower Division Metallurgy/Materials Students
Authors: Guard Ray W. , Stafford S. W.
Published: March 2011

Opportunities in the materials science and engineering field appear quite plentiful into the next century. An increasing number of materials engineers will be needed by industry to develop new materials as well as adapt current ones to new needs. Is there a shortage of metallurgical/materials engineers? Academic institutions with existing or developing programs in materials may affect significant increases in enrollment by “marketing” materials high technology. The Department of Metallurgical Engineering at The University of Texas at El Paso has made exceptional progress in recruiting and retaining prospective engineering students into this technical area. What has been successful at UTEP may also benefit other academic programs.
Concentration Measurements of Chlorine Atoms in A Plasma Reactor
Authors: Wormhoudt Joda , Stanton Alan C. , Richards Albert D. , Sawin Herbert H.
Published: March 2011

Infrared absorption spectroscopy has been used to measure atomic chlorine concentrations over a range of plasma conditions in both Cl2 and CF3Cl discharges.These measurements were made utilizing the spin-orbit transitions in the ground state of atomic chlorine near 882 cm−1.The concentration studies were performed by passing light from a diode laser through a multi-pass (White) cell set in two opposed windows of a parallel plate plasma etching reactor.The plasma work was preceded by a laboratory measurement of the infrared absorption line strengths of the 2P1/2 ← 2P3/2 transition.This measurement was done in a known concentration of atomic chlorine produced in a low pressure discharge flow system by the reaction of Cl2 or HCl with excess fluorine atoms.These measurements resulted in an integrated line strength of 4.14 (±0.89) × 10−21 cm2-molecule−1-cm−1 for the strongest hyperfine component of the transition at 882.3626 cm−1.

Measured atomic chlorine concentrations in Cl2 discharges varied between 0.2 and 8.0 × 1014 atoms/cm3, representing atomic chlorine fractions on the order of a few percent.The measured atomic chlorine concentrations increased approximately linearly with increasing power and pressure, and increased with increasing frequency above approximately 1 MHz.Below 1 MHz, the atomic chlorine concentration was relatively independent of frequency.
Spectroscopic Diagnostics and Kinetics of Low Pressure Processing Plasmas
Authors: Garscadden Alan
Published: March 2011

A review is presented of a negative glow model of low frequency, low pressure plasma reactors and the salient features are described using silane mixtures as the example.The input requirements for this model and similar models are also discussed in order to establish the sensitivity of the homogeneous plasma reactions to operational conditions.Calculations are presented to demonstrate the sensitivity to mixture ratios, buffer gas type and power loading.
An Investigation of the Cathode Fall
Authors: Doughty D. A. , Lawler J. E.
Published: March 2011

Spectroscopic diagnostics are used to map key parameters of the cathode fall of a He glow discharge.Optogalvanic spectroscopy on Rydberg atoms is used to perform spatially resolved electric field measurements.The resulting E/N maps provide the ion and electron current densities, which are used to determine the local ionization rates.Local excitation rates are mapped by observing the spectral emission from the discharge.Optogalvanic spectroscopy is also used to observe electron avalanches starting from a well defined position in the cathode fall.These detailed experimental maps will be essential in studies of the nonhydrodynamic electron distribution function.Various theoretical models of the cathode fall will be compared to the experimental results.
Chemical and Mechanical Properties of Hydrogenated Amorphous Silicon Nitride Films Deposited in Various PECVD Systems
Authors: Kanicki Jerzy , Voke Nancy
Published: March 2011

Hydrogenated amorphous silicon nitride films, prepared in various commercially available plasma enhanced chemical vapor deposition systems, have been investigated in terms of different deposition conditions.The full characterization of these gate insulators has been carried out by different techniques.Experimental data and interesting findings obtained from this study are presented.Indeed, some valuable relationships between physico-chemical and mechanical properties have been established.Special attention has been devoted to the influence of hydrogen on these properties.
Silicon Nitride from Microwave Plasma: Fabrication and Characterization
Authors: Tessier Yves , Klemberg-Sapieha J. E. , Poulin-Dandurand S. , Wertheimer M. R.
Published: March 2011

Plasma silicon nitride (P-SiN) films were prepared from SiH4/NH3 mixtures in a large volume microwave plasma (LMP) apparatus, at substrate temperatures T2 ranging from ambient to 250°C.Under otherwise nominally identical fabrication conditions, deposition rates were 10 to 25 times greater than those reported by others for radio- or audio-frequency plasmas.Based on film compositions, determined by elastic recoil detection (ERD), and measurements of such properties as density, refractive index, etch rate in dilute HF, and moisture permeation coefficient, our best P-SiN films (produced at T2 ≥ 200°C) are very similar to those reported in the literature.
Characterization of Hydrocarbon Plasma used for a-C:H Deposition
Authors: Wagner J. , Wild Ch. , Bubenzer A. , Koidl P.
Published: March 2011

Optical emission analysis and mass spectroscopy was applied to study the rf-glow discharge in hydrocarbons used for the deposition of amorphous hydrogenated carbon (a-C:H).The mass spectra of the positively charged ions in the plasma are characteristic for the hydrocarbon used - e.g.benzene, hexane, or methane.In contrast, the properties of the deposited a-C:H film, such as refractive index, are independent of the precursor gas.Spatially resolved optical measurements show strong emission from C, C2, and CH in the vincinity of the negatively self-biased cathode (substrate) irrespective of the precursor used.Based on these findings we conclude that the fragmentation of the impinging energetic hydrocarbons is one of the key mechanisms for the formation of hard, strongly cross-linked a-C:H films.
Theoretical and Computational Problems in Modeling Glow Discharges
Authors: Graves David B. , Jensen Klavs F.
Published: March 2011

It is desirable to develop detailed models of glow discharge chemical reactors in order to understand the many complex interactions that govern reactor performance.One important part of an overall model of the plasma reactor is the description of the discharge physical structure including charged particle densities, energies and the self-consistent electric field.The continuum or fluid equation approach to this problem is presented in this paper and potential problems with this approach are discussed.Results from recent simulations of a 13.56 MHz rf discharge are presented.The behavior of the electrons in the quasineutral plasma and their interaction with the self-consistent field are highlighted.It is shown that the rf power dissipation peaks at the plasma-sheath boundary, and the implications of this for the validity of estimates of mean electron density from equivalent rf rcircuit models is discussed.
Continuum Modeling of Charged Particle Transport: RF Breakdown and Discharges of SF6
Authors: Thompson Brian E. , Sawun Herbert H. , Owens Aaron
Published: March 2011

Continuity equations for the concentration of electrons, positive ions, and negative ions were constructed and solved to predict rf breakdown voltages and the electrical properties of SF, discharges.These balances for the three types of charged species include terms for convection (electric field-driven fluxes), diffusion, and reactions (ionization, electron attachment, and negative-positive ion recombination).The mobilities, diffusivities, and reaction rate coefficients necessary for the rf discharge model are based on reported measurements and calculations of these parameters in dc electric fields.The electric fields developed in the rf discharge are calculated from Poisson's equation and applied voltage conditions.Predictions based on this model are compared with measured rf breakdown characteristics of SF6.
Kinetics of Plasma Etching Silicon with Nitrogen Trifluoride
Authors: Stenger Harvey G. , Akiki G. S.
Published: March 2011

A kinetic model, composed of elementary chemical reactions, is derived to predict the etch rate of crystalline silicon with NF3 in a plasma discharge.Experimental data taken from a radial flow plasma etching reactor is used to determine the model's kinetic parameters.The rate constant for atomic fluorine reacting with <100> silicon was determined to be 1410 cm/min at 25 °C, in good agreement with a value obtained by other investigators.
Directional Plasma Etching of Polysilicon in SF6/CFCL3 discharges
Authors: Mocella Michael T. , Thompson Brian E. , Sawin Herbert H.
Published: March 2011

The directional etching of P-doped polysilicon has been studied as a function of power (0.2 – 0.8 W/cm3), pressure (0.2 – 0.4 torr), and CFC13 (FreonR-11) fraction (1 – 20%) in SF6 discharges.Over this parameter space, experimental measures of the etching rate, directionality, plasma impedance, optical emission, and ion-bombardment energy and flux were made.Through Ar actinometry, the concentrations of F and Cl were estimated.Response Surface Methodolgy was used to fit the measurements to polynomial models which were used in the subsequent kinetic modeling of the process.As the fraction of CFCl3 was increased from 1 to 20%, the F concentration fell by a factor of 3 while the Cl concentration increased by a factor of approximately 20.The mask undercut and etching rate, however changed less than a factor of two with the CFCl.increase.The measured average ionbombardment energies were well correlated using discharge currents.
Electron Energy Distribution Functions in RF Molecular Plasmas
Authors: Dilonardo M. , Capitelli M. , Winkler R. , Wilhelm J.
Published: March 2011

Electron energy distribution functions in molecular rf plasmas (CO, SF6) have been calculated by numerically solving the time dependent Boltzmann equation in a wide range of field frequencies up to the establishment of the periodic state.Particular attention is given to the reduction of the modulation degree and phase shift with respect to the rf field of the isotropic distribution function and of some macroscopic quantities as a function of frequency.Time averages of distribution functions and of some macroscopic quantities are then compared with the corresponding results obtained by using the effective field approximation.Finally we discuss the role of the second kind collisions in affecting the results.
Single Wafer, Anisotropic Etching of Polysilicon with C12/SF6 and Trielectrode Reactor Operation
Authors: Nulty James E.
Published: March 2011

A totally anisotropic, highly selective dry poly etch process has been developed that is capable of etching sub-2.0 micron linewidths.Doped poly etch rates of 10,000 A/min.are obtained using C12-only chemistry.Standard novolac or bilevel photoresist is used, depending on the lithography requirements.Anisotropy is achieved without the use of carbon-containing gases; as a result, minimal proximity effects are observed between dense and stand alone etched lines.Wafer maps of etched linewidths on 4-inch wafers are presented, showing mask to final bias and uniformity results.

A commercially available triode dry etching system was used for the work.The self-induced dc bias voltage can be selected regardless of the applied rf power.The effect of variable self-induced dc bias versus applied rf power is presented for selectivity, upper and lower electrode interactions, and etch rate uniformity.Characterization by the use of spectroscopy is also presented, showing changes due to varying the self-induced dc bias at a constant rf power.
Homogeneous and Heterogeneous Chemistry of Methane Deposition Plasmas
Authors: Partlow W. O. , Kline L. E.
Published: March 2011

Experimental measurements and theoretical modeling of methane deposition plasmas have made it possible to determine the most likely homogeneous and heterogeneous chemical reaction paths leading to deposition of hydrogenated carbon from the fragments of electron dissociated methane.The methane plasma was modeled as a plug-flow reactor.Gas phase reactions, diffusive transport, variable surface reflection coefficients, and surface chemical reactions are included in the model which follows a “plug” of gas as it flows through the reactor.Boltzmann equation and Monte Carlo calculations were used to determine the electron energy distribution and the resulting dissociation and ionization rate coefficients averaged over space and time.Experimental measurements of the time dependent electrical properties of the plasma are used as input to the model.Deposition rates, deposition uniformity, downstream mass spectroscopy, and the dependences of these quantities on power and mass flow rates are compared to the model to arrive at a consistent representation of the deposition chemistry.
Characterization of Plasma-Enhanced Chemical Vapour Deposition of Silicon-Oxynitride
Authors: Hoek W. G. M. Van Den
Published: March 2011

The plasma-enhanced chemical vapour deposition (PECVD) of siliconoxynitride from silane, ammonia and nitrous oxide was studied using an ASM vertical parallel plate reactor.Films varying from PECVD oxide (refractive index no1.50) to PECVD nitride (n=2.00) were analyzed using ellipsometry, UV-visible reflection spectroscopy, Fourier-transform infrared transmission spectroscopy (FTIR), nuclear reaction analysis (NRA), Rutherford backscattering (RBS) and electron spectoscopy for chemical analysis (ESCA).Stress measurements were performed using a Fizeau interferometer.
Influence of Substrate Temperature on the Structure of Tin-Films
Authors: Molarius J. M. , Korhonen A. S. , Erola E. , Nykanen E.
Published: March 2011

Three series of Ti-N films with varying nitrogen contents from about 8 to 52 at.% N were deposited by triode ion plating at temperatures of 773, 623 and 373 K, respectively.Marked changes in the structures of the films with decreasing temperature were observed by x-ray diffraction.Stoichiometric δ-TiN which showed (220) preferred orientation at 773 K changed to (111) at lower temperatures.At intermediate nitrogen concentrations α-Ti (002) decreased and a new ε-Ti2N (002) developed with decreasing temperature.Very smooth and dense films could be produced at the lower temperatures.
Rie-Induced Damage to Single Crystal Silicon Monitored with Nondestructive Thermal Waves
Authors: Geraghty Patrice , Smith W. Lee
Published: March 2011

A method is presented to nondestructively monitor damage in silicon caused by reactive-ion or plasma etching on actual product wafers or test wafers immediately following the etch step.Data is taken on product wafers by scanning the 1-micron laser probe spot across and along the bottom of RIE-etched trenches.The onset of silicon damage brings a marked increase to the thermal wave (TW) signal: as the RIE bias voltage was increased from -60 volts to -250 volts, the TW signal increased monotonically by 1230%.The effects of other RIE process parameters on the damage level were also measured.This study allowed the RIE process variables to be adjusted to minimize damage to the silicon surface.
The Chemical Etch of Tungsten Single Crystals and Foils With XeF2
Authors: Bensaoula A. , Stozier J. , Ignatiev A. , Wolfe J.
Published: March 2011

The chemical etching of W(100) single crystals and polycrystalline tungsten foils using a XeF2 molecular beam has been studied with and without simultaneous bombardment by energetic inert ions.The surface fluorine concentration, measured under different XeF2 pressures (10−7 to 10−5 torr) and ion current densities, is found to be always less than a monolayer.Depth profiles of the fluorine layer show that in both single crystal and poly samples, the fluorine is surface localized, although slightly deeper in the W(100).A kinetic model is presented to account for the enhanced etching under ion bombardment.The mechanism proposed is mainly a defect driven enhancement of the etch yield.This model is consistent with both the fluorine concentrations measured in this work as well as the etch product yields reported by Winters.
The Effects of ion Bombardment in Plasma Polymerization
Authors: Buss Richard J.
Published: March 2011

A molecular beam probe technique has been used to investigate the role of ion bombardment of the film surface during the plasma polymeriz-ation process.Thin films have been deposited in a vacuum chamber from a molecular beam containing all the plasma species and these were compared with similar deposits from a beam with the charged particles deflected away.A comparison was made of deposition rates, vis/UV and IR absorption spectra of the films.It was found that the deposition rate was increased 20% with the elimination of ion bombardment.Ions incident on the film surface during deposition cause a net ablation of the film.The ion bombardment also causes an increased absorption of UV and near UV light by the film resulting in a noticeable yellowing.No change was observed in the IR spectra of the films with ion deflection.
Reactive Ion Etching of WSi0.6 Gates for GaAs MESFETS
Authors: Lin C. L. , Hoh Peter D.
Published: March 2011

A process for reactive ion etching of 1μm and sub-micron WSi0.6 gates for GaAs MESFET integrated circuits has been developed.Using a CF4/O2 plasma, a 200am film of WSi0.6 could be etched in ≃ 5 minutes.This is sufficiently long for accurate process monitoring.A vertical edge profile has been obtained which is desirable for a self-aligned MESFET process.To achieve the vertical edge, careful control of the degree of over etch was necessary.This was accomplished by monitoring the intensity profile of a laser beam reflected from the wafer being etched.The widths of lines etched in WSi0.6 closely matched those of the resist pattern.Both 1μm and sub-micron FET's were fabricated.with excellent linewidth control and electrical characteristics
Reactive Ion Etching of Molybdenum In CF4/O2 Plasma
Authors: Park Seong-Ju , Sun C. P. , Yeh J. T. , Cataldo J. K. , Metropoulos N.
Published: March 2011

A mechanistic study of Mo etching in a CF4/O2 plasma has been performed using optical emission spectroscopy, mass spectrometry and x-ray photoelectron spectroscopy.Etching characteristics of Mo for a wide range of conditions relevant to plasma processing are also reported.Addition of small amount of O2 to the CF4 plasma dramatically increases the Mo etch rates, as well as concentrations of 0 and F in plasma.However, further addition of O2 above 50 % leads to decrease in etch rates.Two types of neutral molybdenum oxifluorides and a trace amount of molybdenum hexafluoride were observed in the effluent gas.Comparing the etch rates with the concentration changes of F and 0 with and without Mo present in plasma, it is suggested that Mo is chemically etched by F and 0.Atomic oxygen enhances the etch rate by increasing the F concentration in the plasma as well as by removing a carbon layer forming desorbed CO on the surface.XPS and AES analysis results for the etched surface inferred that chemisorbed fluorocarbon radicals dissociate into carbon and fluorine atoms, which in turn form a passivating graphite-like layer and a volatile molybdenum oxifluoride and molybdenum hexafluoride layer.
The ETCH Mechanism for Al2O3 in Fluorine and Chlorine Based RF Dry Etch Plasmas
Authors: Hoek W. G. M. van Den
Published: March 2011

The etch behaviour of Al2O3 was studied in Ar, CHF3/Ar, CF4/O2 and Cl2 low pressure RIE plasmas.The influence of dc self-bias voltage, wafer temperature, gas flow and pressure on the Al2O3 etch behaviour was investigated.This was compared with the etch behaviour of SiO2, Mo, Au and Si under the same conditions.It was found that even though aluminum does not form volatile fluorides addition of CHF3 to an Ar plasma resulted in a ninefold increase in the A12O3 etch rate.This compares to a fivefold increase in the SiO2 etch rate and a 20% decrease in Au etch rate.

An A12O3 etch mechanism for fluorine based plasmas is proposed, comprising of the formation of AlFx and its subsequent removal under influence of high energy ion bombardment.The latter appears to be the rate limiting step.