bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and mechanical properties of Ti–Si–C coatings deposited by magnetron sputtering
Authors: Koutzaki S. H. , Krzanowski J. E. , Nainaparampril J. J.
Published: July 2002

Nanostructured coatings consisting of mixed carbide phases can provide a potential means to developing superhard coatings. Heterogeneous nanostructured coatings can be obtained by either deposition of multilayer structures or by depositing film compositions that undergo a natural phase separation due to thermodynamic immiscibility. In the present work, we have taken the latter approach, and deposited films by radio frequency cosputtering from dual carbide targets. We have examined a number of ternary carbide systems, and here we report the results obtained on Ti–Si–C films with a nominal (Ti1−xSix)C stoichiometry and with x⩽0.31. It was found that the nanoindentation hardness increased with Si content, and the maximum hardness achieved was nearly twice that of sputter-deposited TiC. We further analyzed these films using high-resolution transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction. Since cubic SiC has an x-ray pattern almost identical to that of TiC, the extent of phase separation could not be determined by that method. However, XRD did demonstrate a general disordering of the films with increasing SiC content. In addition, a mottled structure was observed in high-resolution TEM images of the Si-containing films, confirming microstructural effects due to the Si additions.
Free jets in vacuum technologies
Authors: Rebrov A. K.
Published: July 2002

The interest in jets expanding into a vacuum or a low-density background is raised by the appearance of new technological methods and growing requirements of high technology development. The use of free jets for vacuum technology, including space applications, has a number of aspects. One of the important achievements of the previous investigations is an understanding of jet structures in a variety of gas dynamic conditions. The accumulated knowledge on radial expansion into a vacuum, on the expansion of jets behind axially symmetric and flat sonic, and supersonic nozzles into a vacuum and background from the literature can be used for approximate evaluations. At present, more detailed data can be obtained as the result of computational modeling by continuum and kinetic approaches. Modern gas dynamics has at its disposal effective theoretical methods that open wide possibilities for vacuum technology development. The present article reflects the accumulated knowledge on the structure of jets, calculation of jet parameters, and modern trends in the analysis of low density jets.
Silicon on GaN(0001) and (0001̄) surfaces
Authors: Lee C. D. , Feenstra R. M. , Rosa A. L. , Neugebauer J. , Northrup J. E.
Published: July 2002

Surface reconstructions and adatom kinetics of silicon on GaN(0001) and (0001̄) surfaces are studied by scanning tunneling microscopy, electron diffraction, and first-principles calculations. For silicon coverage near 0.5 monolayer, a 2×2 structure is observed, and is interpreted in terms of a model consisting of a Ga adatom on a monolayer of 3 Ga+1 Si and a SiGa atom in the third layer. For higher silicon coverage, disordered 2×2 domains and “1×1” domains are found to coexist. After annealing above 300 °C the “1×1” regions become dominant and a 4×4 structure is seen near step edges. It is concluded that the silicon adatoms tend to reside in subsurface sites on the Ga-polar surface. Surface morphology in the presence of Si is smooth for the (0001) surface but rough for the (0001̄) surface. This difference is attributed to the presence of multiple Ga surface layers in the former case, which enhance surface diffusivities.
Faceting transition in epitaxial growth of dilute GaNAs films on GaAs
Authors: Adamcyk M. , Tixier S. , Ruck B. J. , Schmid J. H. , Tiedje T. , Fink V. , Jeffries M. , Karaiskaj D. , Kavanagh K. L. , Thewalt M.
Published: July 2002

An abrupt transition to a {111} faceted growth mode is observed in molecular-beam-epitaxy growth of dilute GaNxAs1−x (x<0.05) films on (100) GaAs substrates. The faceted growth mode is favored by high growth temperatures, high nitrogen content, and high arsenic flux. The best electronic quality material, as measured by low-temperature photoluminescence, was obtained at high growth temperatures and high arsenic flux without exceeding the threshold for facet formation. The nitrogen content was found to be insensitive to the arsenic flux.
Structure shape and stability of nanometric sized particles
Authors: Yacamán M. José , Ascencio J. A. , Liu H. B. , Gardea-Torresdey J.
Published: July 2002

Nanoparticles are a state of matter that has properties different from either molecules or bulk solids. In the present work, we review the shape and structure of nanometer-sized particles; several shapes are discussed, such as the octahedron and truncated octahedron, the icosahedron, the Marks decahedron, the truncated “star-like” decahedron, the rounded decahedron and the regular decahedron. Experimental high-resolution transmission electron microscopy (TEM) images of each type of particle are presented together with the Fast Fourier Transform and a model of the particle. We consider only gold particles grown by vapor deposition or by colloidal methods. High-resolution TEM images of the particles in different orientations are shown. We discuss two basic types of particles uncapped and capped. Data for other metals and semiconductors are reviewed. We have also performed very extensive simulations obtaining the total energy and pair correlation functions for each cluster under study. Furthermore, distributions of single atom energy for every cluster are displayed in order to reveal the effect of surface on the stability of different types and sizes of clusters. We discuss the structure of the particles from ∼1 to ∼100 nm. The mechanisms for stress release as the particles grow larger are reviewed and a mechanism is suggested. Finally, we discuss the parameters that define the shape of a nanoparticle and the possible implications in technological applications.
Transition to insulating behavior in the metal-semiconductor digital composite ErAs:InGaAs
Authors: Driscoll D. C. , Hanson M. , Kadow C. , Gossard A. C.
Published: July 2002

Superlattice structures of semimetallic ErAs particles embedded in an InGaAs matrix were fabricated on (001) Fe doped InP substrates with varying amounts of ErAs. The samples were characterized by temperature dependent Hall measurements, x-ray diffraction, and transmission electron microscopy. The temperature dependence of the mobility, charge density, and sheet resistance is presented. The apparent offset between the conduction band minimum of the InGaAs matrix and the Fermi energy of the ErAs particles is strongly dependent on the amount of ErAs deposited. The offset is determined from the measured charge density and the InGaAs density of states. As the size of the ErAs particles increases, the Fermi level decreases from ∼0.01 eV above the InGaAs conduction band edge to ∼0.15 eV below the InGaAs conduction band edge and the electrical conduction properties change from metallic to semiconducting.
Review of progress in extreme ultraviolet lithography masks
Authors: Hector Scott , Mangat Pawitter
Published: July 2002

Extreme ultraviolet lithography (EUVL) is a leading next generation lithography technology. Significant progress has been made in developing mask fabrication processes for EUVL. The mask blank for EUVL consists of a low thermal expansion material substrate having a square photomask form factor that is coated with Mo/Si multilayers. SEMI standards are being developed for mask substrates and mounting. Several commercial suppliers are developing polishing processes for LTEM substrates, and they are progressing toward meeting the requirements for flatness, surface roughness, and defects defined in the a draft SEMI standard. One of the challenges in implementing EUVL is to economically fabricate multilayer-coated mask blanks with no printable defects. Significant progress has been made in developing mask blank multilayer coating processes with low added defect density. Besides lowering the added defect density, methods to reduce defect printability, such as defect compensation and buffer layer smoothing, are being developed. Experiments indicate that Mo/Si multilayers that are deposited with ion beam deposition tend to smooth substrate defects, and buffer layer films are being designed to enhance this effect. Targets for buffer layer smoothing are being defined using defect printability simulations. A method for using an electron beam to repair substrate defects after multilayer coating is also being investigated. The mask patterning process for EUVL is nearly the same as that for conventional binary optical lithography masks. EUVL mask patterning efforts are focused on developing the EUV-specific aspects of the patterning process. Eight absorbers have been evaluated against the requirements for EUVL masks, and two absorbers appear most promising. Conventional membrane pellicles are not practical for EUVL, so thermophoretic protection is being developed. Experiments have indicated that thermophoretic protection is effective for >125 nm particles down to at least 50 mTorr pressure. A removable pellicle will be used to protect the mask from defects at all times except during wafer exposure.
Photoemission study of energy-band alignments and gap-state density distributions for high-k gate dielectrics
Authors: Miyazaki Seiichi
Published: July 2002

The determination of the energy band gaps of thin-gate insulators has been demonstrated from the onsets of the energy-loss spectra of O 1s (or N 1s) photoelectrons. The valence-band lineups of thin high-dielectric-constant (high-k) dielectrics such as Ta2O5, Al2O3, and ZrO2 formed on metals and Si(100) have also been determined by measuring the energy difference between the valence-band density-of-states curves. The energy band diagrams for metal/high-k dielectrics/Si(100) systems have been derived explicitly from considering the measured band gaps, valence-band lineups, electron affinities, and metal work functions in the systems. It is also demonstrated that total photoelectron yield spectroscopy can be used to quantify the energy distributions of both the defect states in high-k gate dielectrics and at the dielectric/Si(100) interfaces over the entire Si band gap without gate formation.
Can proximity x-ray lithography print 35 nm features? Yes
Authors: Khan Mumit , Han Geng , Tsvid Gene , Kitayama Toyoki , Maldonado Juan , Cerrina Franco
Published: July 2002

We report on the results of our effort to extend proximity x-ray lithography (PXL) to 35 nm using a harder energy spectrum, and choosing the appropriate materials for the mask and the resist to match the transmission and absorption at higher energies. Previous studies [M. Kahn et al., J. Vac. Sci. Technol. B 17, 3426 (1999); T. Kitayama, J. Vac. Sci. Technol. B 18, 2950 (2000)] have shown that PXL is capable of printing 50 nm features, and in this study, we extend that work to show that PXL can indeed be used for 35 nm generation. We investigate the use of higher energy radiation, in conjunction with novel resist materials, to deliver the 35 nm node and provide a set of requirements to achieve that goal.
Etching characteristics and plasma-induced damage of high-k Ba0.5Sr0.5TiO3 thin-film capacitors
Authors: Wuu D. S. , Lin C. C. , Horng R. H. , Liao F. C. , Liu Y. H.
Published: July 2002

The inductively coupled plasma (ICP) etching behavior of Ba0.5Sr0.5TiO3 (BST) thin films has been characterized with Cl2/Ar gas mixtures by varying the process parameters such as chamber pressure, ICP power, and substrate bias rf power. The etching characteristics of BST were investigated in terms of etch rate, etch profile, surface residue, and electrical properties. The results obtained can be further interpreted by the plasma properties (ion flux and dc bias) in situ measured by a Langmuir probe. Quantitative analysis of the plasma-induced damage in the Pt/BST/Pt capacitor was attempted to discuss the mechanism of leakage current density and dielectric constant with various substrate bias rf power and ICP power levels. Finally, optimization of the etch parameters for fabricating BST capacitors was performed to minimize the plasma-induced damage. The optimum condition appears to be under a 30% Cl2/(Cl2+Ar) gas mixture, ICP power of 800 W, substrate bias rf power of 100 W, and chamber pressure of 0.67 Pa. Furthermore, it is found that the damage samples can be effectively recovered after annealing at 600 °C in oxygen ambient. The result can be confirmed by the x-ray diffraction data, which indicates that an improvement of BST crystalline quality after annealing occurs. This makes the leakage current density of the Pt/BST/Pt capacitor decrease to 3×10−7 A/cm2 under an applied voltage of 1.5 V, while its dielectric constant can recover from 150 to 180.
Nanoimprint lithography of high-density cobalt dot patterns for fine tuning of dipole interactions
Authors: Natali M. , Lebib A. , Cambril E. , Chen Y. , Prejbeanu I. L. , Ounadjela K.
Published: July 2002

A trilayer nanoimprint process was used to fabricate high-density Co dot arrays. It is shown that choosing hybrane as the top layer resist gives better dimensional control of the replicated patterns compared to PMMA. By adjusting the etching time in the transfer process the dot sizes could be tailored in a wide range. The fabricated dot arrays with different sizes and period have then been studied by magneto-optic and magnetic-force microscopy measurements. The magnetization reversal was found to occur through vortex nucleation/annihilation. Dipolar interactions were clearly identified both in arrays with constant dot diameter and variable period and in arrays with fixed period and variable dot diameters. In the case of closely packed dots vortex chain structures along the field direction can be formed as a consequence of a nucleation cascade process.
Morphological transition of Si1−xGex films growing on Si(100). II. Synchrotron-radiation-excited chemical-vapor deposition: From two-dimensional growth to growth in the Volmer–Weber mode
Authors: Akazawa Housei
Published: July 2002

The morphological evolution of Si1−xGex films growing under conditions of excitation by high-energy photons (hν>100 eV) has been investigated by means of in situ spectroscopic ellipsometry. An atomically discontinuous wetting layer is produced by the incidence of the products of photolysis from Si2H6 and GeH4 on a hydrogen-terminated Si(100) surface. At temperatures of growth below 300 °C, a uniform Si1−xGex layer grows because of the strong hydrogen surfactant effect and the low mobility of the Si and Ge adatoms. At temperatures above 400 °C, most of the Si adatoms are in the form of monohydride and Ge adatoms are free of bonds with hydrogen atoms. On a partially hydrogen-covered surface, the number of dangling-bond terminated nucleation centers is restricted, while the migration of the adatoms is enhanced. This results in islanding with roughness up to a maximum height of about 100 Å from the initial stages of growth. Since the grain boundaries between islands become the sources of dislocations, the strain stored in the Si1−xGex islands is completely relieved. This leads to early coalescence so that a flat overlayer surface is recovered.
Plasma-enhanced chemical-vapor deposition of titanium aluminum carbonitride/amorphous-carbon nanocomposite thin films
Authors: Shieh Jiann , Hon Min Hsiung
Published: July 2002

A new nanocomposite, titanium aluminum carbonitride/amorphous-carbon thin film was prepared by radio-frequency (rf) plasma-enhanced chemical-vapor deposition using titanium tetrachloride, aluminum trichloride, methane, and nitrogen as reactants. Hydrogen was used as carrier gases. A substrate temperature of 500 °C and an rf power of 100 W were used in all depositions. The films were characterized by x-ray powder diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. The results show that nanograins of titanium aluminum carbonitride were embedded in an amorphous-carbon matrix. The nanograins had a (200) preferred orientation with columnar cross-section morphology. Mechanical properties were analyzed by nanoindentation and hardness was demonstrated to increase via this microstructure design approach. The effects of microstructure on mechanical properties were also determined.
Optical properties of magnesium fluoride thin films produced by argon ion-beam assisted deposition
Authors: Dumas L. , Quesnel E. , Pierre F. , Bertin F.
Published: July 2002

Magnesium fluoride thin films were deposited on silica glass and single crystal silicon substrates by argon ion-beam assisted deposition (IBAD). The effects of argon ions impinging on the growing film on the optical and chemical properties of the single layers were investigated. Compared to MgF2 films produced by direct electron-beam evaporation, the films obtained by IBAD exhibited increased optical absorption and refractive indices, fluorine depletion and increased oxygen contamination. Optical data were analyzed and are discussed with regard to the chemical composition of the films.
Defect engineering: An approach on ultrashallow junction in silicon
Authors: Shao Lin , Lu Xinming , Wang Xuemei , Rusakova Irene , Liu Jiarui , Chu Wei-Kan
Published: July 2002

Fabrication of sub-100 nm junctions in ultralarge scale integration becomes extremely difficult due to anomalous diffusion of B in Si. By judiciously placing vacancy and interstitial defects at different depths by implantation of Si ions with different incident energies and dosages in Si, B diffusion can be enhanced or retarded. After preimplantation with 50 or 500 keV Si+ ions to produce surface vacancy-rich regions, Si samples were B deposited and annealed at various temperatures between 900 and 1010 °C. B diffusion retardation was observed in both implantation conditions after low temperature annealing, while B diffusion enhancement occurred in 50 keV implanted samples after annealing at a high temperature. Choosing high energy implantation to separate vacancies and interstitials can reduce the boron diffusion significantly. Such suppression became more obvious with higher implant dose. Junctions less than 10 nm deep (at 1×1014 cm−3 by carrier concentration profiles) can be formed.
Dry etching of amorphous-Si gates for deep sub-100 nm silicon-on-insulator complementary metal–oxide semiconductor
Authors: Yost D. , Forte T. , Fritze M. , Astolfi D. , Suntharalingam V. , Chen C. K. , Cann S.
Published: July 2002

Sub-100 nm gates are fabricated for fully depleted silicon-on-insulator complementary metal–oxide semiconductor transistor and circuit fabrication using optical lithography and a high density, transformer coupled plasma etch process. The antireflective coating (ARC) bake temperature and HBr/Cl2/O2 organic ARC etch chemistry were optimized to maintain device critical dimension. The amorphous silicon (a-Si) main etch uses HBr/Cl2/He/O2 and was optimized at a high HBr concentration, high temperature, low O2 concentration, and a low pressure to obtain minimal CD bias and maximum selectivity to both oxide and resist. Main Etch end-point determination was developed to trigger on a rising Cl2 reactant optical emission signature at 510 nm avoiding interference from CO lines at typical end-point determination wavelengths for integration using resist masks with a high percentage of resist area. Transistors were fabricated with gate lengths of 25 and 50 nm.
Electron dynamics in unoccupied molecular orbitals of two blue-light-emitting organic electroluminescent materials
Authors: Karlsson H. S. , Read K. , Haight R.
Published: July 2002

The lowest unoccupied molecular orbital (LUMO) in the two blue-light-emitting organic luminescent materials bis(2-methyl-8-quinolinolato)(para-phenyl-phenolato)aluminum and 1,4-bis(2,2-diphenylvinyl)biphenyl was studied by femtosecond laser pump-and-probe photoemission and compared with tris(8-hydroxyquinoline)aluminum. We have determined the energy gap between the LUMO and the highest occupied molecular orbital and studied the LUMO decay dynamics in these materials. The differences in decay rates are shown to be related to the morphology of the evaporated films.
Study of InGaP/GaAs/InGaAs high-barrier gate and heterostructure-channel field-effect transistors
Authors: Yu Kuo-Hui , Lin Kun-Wei , Lin Kuan-Po , Yen Chih-Hung , Wang Ckih-Kai , Liu Wen-Chau
Published: July 2002

A heterostructure field-effect transistor with an n+-GaAs/p+-InGaP/n-GaAs high-barrier gate and n-GaAs/i-InGaAs/i-GaAs/delta-doped sheet heterostructure channel (device A) has been successfully fabricated and studied. The heavily doped p+-InGaP layer and heterostructure channel are introduced to increase the barrier height and carrier confinement, respectively. Experimentally, the device without the high-barrier gate structure (device B) is also fabricated for comparison to investigate the influence of high-barrier gate structure on device characteristics. Due to the high-barrier gate added to suppress the tunneling current in device A, the gate leakage current is also substantially reduced. Therefore, the turn-on voltage, breakdown voltage, current drivability, and transconductance linearity are all significantly improved for device A relative to device B. Furthermore, the temperature-dependent characteristics of device A are also improved.
Abstract: Intense field-emission ion source of liquid metals
Authors: Clampitt R. , Aitken K. L. , Jefferies D. K.
Published: July 2002

Intense ion beams are of interest in fusion research for plasma heating, diagnostics, and target compression and in industry for implantation, microfabrication, etc.

We report the generation of intense beams of metal ions of Li, Cs, Sn, Ga, and Hg by field-ion emission of molten metal films on solid wire needles. The source is extremely simple and is based on electrohydrodynamic instabilities induced in liquid films under electric stress. In practice, for a point-source or needle emitter, a tungsten needle protrudes from the surface of the molten metal which, with good wetting, flows as a thin film to the needle apex. Application of a potential difference between the needle anode and an apertured cathode results in an electrohydrodynamic instability in the film which is manifested as a filamentary cusp at the needle apex. The electric field intensity at the cusp is sufficient to produce intense atomic-ion emission by field ionization. When the protruding length of the needle through the molten metal pool is appropriately adjusted, the tip becomes self-feeding and continuous ion emission occurs.

Direct currents of 50–700 μA can be readily produced from single needles at modest voltages (3–10 kV). Examination of the liquid cusp in an electron microscope shows that the radius of the emitting zone is ?104 Å, suggesting ion current densities in excess of 104 A/cm2. Source scaling can be achieved with an array of needles. Alternatively, one can use a linear or annular edge over which the molten metal flows as a thin film. In the latter source the ion emitting sites are generated along the edge by the field at a frequency given by λ=8πS/3ε0E2, where S is surface tension and E is field strength.

Ion emission is accompanied by light emission from a microscopic spot (10–50 μm) at the anode apex. The anode emission process bears some phenomenological similarities to anode spots and cathode spots in vacuum arcs and to pulsed high-current pinched plasma jets formed on pointed anodes or from exploding wires. Such plasmas are known to be dynamic linear pinches. What we have produced is a microscopic metal-vapor plasma ball, and we have found a way of anchoring this to allow continuous operation. We do not know by what mechanism the intense plasma spot forms; almost certainly it is initiated by field ionization, the electrons perhaps being generated by ion collisions with the metal vapor. Heating and evaporation of the anode jet could be by I2R heating or by electrons accelerated across the anode drop between plasma ball and liquid surface.

As a stable plasma ball it is novel and readily lends itself to plasma diagnostics. Also by rapidly discharging a high current at high voltage through the anode it should provide a source of a minute dense plasma more reproducibly than presently attained and an intense pulsed source of ions, light, and x rays.
Definitive pressure generation in the 10−4–10−3 Torr range for atomic scattering experiments
Authors: Van Zyl B. , Chamberlain G. E. , Dunn G. H. , Ruthberg S.
Published: July 2002

A pressure generation technique using the dynamic expansion method is described. Measurements and uncertainties are discussed, and it is shown that the method provides a convenient means for obtaining accurate pressures in the 10−3–10−4 Torr range. High confidence uncertainties as low as about ±1% are achieved.
Transmission electron microscopy of interfaces in III–V compound semiconductors
Authors: Petroff P. M.
Published: July 2002

This paper presents a review of the applications of transmission-electron-microscopy (TEM) analytical techniques to the study of several types of interfaces in III–V compound semiconductor structures. The TEM techniques for analysis of lattice mismatched interfaces are briefly discussed since they are straightforward for most III–V compounds. New techniques for analyzing interface roughness and interface diffusion on an atomic scale are presented. The study of interface structures on such a fine scale is made possible by optimizing the diffraction effects between interfaces and the electron beam. By combining the excellent control of the molecular-beam-epitaxy deposition technique to fabricate ’’interface superlattices’’ with high-resolution dark-field and lattice-imaging TEM techniques, the interface roughness between ultrathin GaAs and AlAs films have been analyzed on an atomic scale. Interdiffusion at GaAs and AlAs interfaces is also discussed, and two methods which make use of ’’interface superlattices’’ are presented. They allow for rapid and precise measurements of diffusion profiles and diffusion length as small as 2.83 Å for this system. The TEM techniques discussed in this paper are applicable to other types of semiconductor structures providing they can be made into ultrathin superlattices.
Comparison of properties of dielectric films deposited by various methods
Authors: Pliskin W. A.
Published: July 2002

In this review paper, the physico–chemical properties of various dielectric films used on semiconductor devices are compared according to their method of formation or deposition. The insulators which are discussed are silicon dioxide, phosphosilicate glass, silicon nitride, alumina, borosilicate glass, and other silicate glasses. The techniques of formation or deposition are thermal oxidation, CVD and pyrolytic deposition, plasma CVD, dc and rf reactive sputtering, rf sputtering, electron beam evaporation, and fused glass from sedimented powders.
Significance of negative ion formation in sputtering and SIMS analysis
Authors: Cuomo J. J. , Gambino R. J. , Harper J. M. E. , Kuptsis J. D. , Webber J. C.
Published: July 2002

An unexpected substrate etching phenomenon during the sputtering of certain intermetallic compounds has been found to be caused by a large flux of negative metal ions from the sputtering target. The substrates directly under the target in a diode geometry are etched (eroded) rather than coated with a film. The occurrence of this substrate etching has been correlated with negative ion yields measured by secondary ion mass spectroscopy (SIMS). We find a high yield of negative metal ions from several intermetallic compounds in addition to the highly ionic compounds previously reported. A model based on electron charge transfer is presented which predicts when negative ion formation will be important, and the dependence of etch rate on target voltage is also treated. We predict that negative ion effects will be found in the sputtering of a wide range of compounds.
Adhesion of copper films on ABS polymers deposited in an internal magnet magnetron sputtering system
Authors: Tsukada Tsutomu , Hosokawa Naokichi
Published: July 2002

In order to metallize ABS polymer surfaces without electroless plating, thin copper films were deposited by an internal magnet, coaxial cylindrical magnetron sputtering system. The adhesion of the metallized layers was evaluated by measuring peel strength. Average strength higher than 1 kg/cm was obtained with an appropriate process of metallizing. Several factors, which might influence the adhesion, such as conditions of sputtering, pretreatment of the polymer before sputtering, and the constitution of the polymer were studied. Oxygen plasma treatment before the metallization was found to improve the adhesion. Topographical change of the polymer surface was observed with SEM for the oxygen-plasma-treated substrate. Also, surface change in atomic constitution and chemical bonding energies were detected by ESCA and ir spectroscopy. It was found that the peel strength was higher for substrates of smaller butadiene content, which implied that tensile strength of polymer affected the peel strength of the metallized layer.
Formation of metal–oxygen–polymer complexes on polystyrene with nickel and chromium
Authors: Burkstrand James M.
Published: July 2002

The microscopic interactions between vapor-deposited nickel and chromium atoms and oxygen-treated polystyrene surfaces were investigated using x-ray photoemission spectroscopy. Exposure to atomic oxygen created single bonds between carbon and oxygen atoms in both C–O–H and C–O–C groups. The resulting O 1s core lineshape shifted from 533.2 to 532.7 eV after deposition of Ni and from 533.6 to 531.9 eV after deposition of Cr. These changes indicate the formation of metal–oxygen–polymer complexes at the interface. The presence of these complexes correlated with an increase in the adhesion of these metal films to the oxygen-treated substrate compared to the clean polystyrene substrate.
Outgassing rate of multilayer insulation materials at ambient temperature
Authors: Glassford A. P. M. , Liu C. K.
Published: July 2002

The ambient temperature outgassing rate of several multilayer insulation materials has been measured for evacuation times of about six days. The material tested included Mylar radiation shields, double and single metallized with aluminum and gold; double and single aluminized Kapton radiation shields of different thicknesses; and three net and two glass fiber-cloth spacer materials. Experimental measurements were made by collecting outgassing flux from an effusion cell-type sample holder on a liquid-nitrogen-cooled quartz crystal microbalance. The absolute accuracy, measurement range, degree of resolution, and other features of this technique are discussed in detail. The physical phenomena controlling outgassing rate are discussed. It is concluded that long-term outgassing of the metallized shields is probably controlled by degassing of the metallized surfaces. On this assumption empirical equations are proposed for estimating long-term outgassing rates. Data from previous measurement programs are evaluated and compared with the new data as a standard.
Construction and performance characteristics of a low cost energy prefilter
Authors: Craig J. H. , Hock J. L.
Published: July 2002

Construction and performance details are presented for a low-cost energy filter (Bessel Box). Comparison is made between two devices of different lengths. The energy resolution of the longer device is shown to be 0.5 eV at a pass energy of 6 eV.
Technology and applications of broad-beam ion sources used in sputtering. Part II. Applications
Authors: Harper J. M. E. , Cuomo J. J. , Kaufman H. R.
Published: July 2002

The developments in broad-beam ion source technology described in the companion paper (Part I) have stimulated a rapid expansion in applications to materials processing. These applications are reviewed here, beginning with a summary of sputtering mechanisms. Next, etching applications are described, including microfabrication and reactive ion beam etching. The developing area of surface layer applications is summarized, and related to the existing fields of oxidation and implantation. Next, deposition applications are reviewed, including ion-beam sputter deposition and the emerging technique of ion-assisted vapor deposition. Many of these applications have been stimulated by the development of high current ion sources operating in the energy range of tens of hundreds of eV. It is in this energy range that ion-activated chemical etching is efficient, self-limiting compound layers can be grown, and the physical properties of vapor-deposited films can be modified. In each of these areas, broad ion beam technology provides a link between other large area plasma processes and surface analytical techniques using ion beams.
Trilayer Raman scattering of variably ordered amorphous Ge
Authors: Yehoda Joseph E. , Lannin Jeffrey S.
Published: July 2002

Interference-enhanced Raman scattering measurements are reported on rf diode sputtered a-Ge as a function of annealing temperature. The results on films ∼50 Å thick indicate a monotonic decrease of the half-width of the TO-like phonon band for the depolarized Raman component as a function of annealing temperature. In addition, the ratio of the TA to TO peak intensities is also found to monotonically decrease with temperature. These results indicate changes in the vibrational spectrum of a-Ge that arise from increasing short range order and parallel studies on thicker a-Ge and a-Si films with deposition conditions. During crystallization the Raman spectra also indicate that the amorphous phase continues to increase its structural order. A comparison with the Raman spectra of thicker films allows an estimate of the optical gap to be obtained in the very thin a-Ge films.
Vacuum plasma spraying of tantalum and niobium
Authors: Lugscheider E. , Eschnauer H. , Häuser B. , Jäger D.
Published: July 2002

Vacuum plasma spraying is a suitable process for producing high quality coatings of reactive metals such as tantalum and niobium. Ta and Nb coatings used for corrosion protection must be extremely dense, homogeneous, and of high purity and adhesion. Hence, the process parameters have to be carefully optimized even with regard to the spraying powder, its grain size and morphology. Spraying equipment with vacuum systems which allow for a final pressure of 10−3 mbar, which have heated and evacuated powder feeder units, and heated substrates, as well as the use of powders with high purity and low gas content, are required for producing high quality Ta and Nb coatings. Corrosion tests in sulfuric acid and aqua regia at different concentrations show that Ta and Nb coatings sprayed under optimized conditions have high resistance to both general and localized corrosion.
Laser-induced gold deposition on a silicon substrate
Authors: Tamir S. , Zahavi J.
Published: July 2002

In recent years, substantial progress in the electronics industry has been witnessed. The growth of this industry led to intensive competition in the field of microelectronic devices and to more rigorous performance requirements with regard to the products. Extensive research has been undertaken with a view to improving the integrated circuits used. The trend today is to miniaturize the devices as much as possible, and one of the main problems involved is realization of metal deposition lines a few microns in width with high width resolution, so that the spacing of adjoining lines would be of the same order with no interaction between them.
Dynamics of recombinative desorption of H2 and D2 from Cu(110), Cu(111), and sulfur-covered Cu(111)
Authors: Kubiak Glenn D. , Sitz Greg O. , Zare Richard N.
Published: July 2002

Rotational and vibrational state distributions have been determined for H2 and D2 recombinatively desorbing from clean Cu(110) and Cu(111) surfaces in ultrahigh vacuum, and also from sulfur-covered Cu(111). A 2+1 resonanced-enhanced multiphoton ionization technique is employed. For clean copper the (v″=1)/(v″=0) vibrational population ratio for both H2 and D2 is ∼50 times greater than the value expected for an equilibrium ensemble at the surface temperature Ts for desorption from Cu(110) and ∼100 times greater from Cu(111). In contrast, for sulfur-covered Cu(111), the H2 (v″=1)/(v″=0) ratio is 10 to 100 times less than for clean Cu(111) at the start of permeation but recovers sharply about 45 min later to a value close to that measured for the clean surface. We find that the total near-surface sulfur concentration appears to remain constant over the same time period, but that the overlayer structure is radically altered.
High rate sputtering deposition of nickel using dc magnetron mode
Authors: Chang S. A. , Skolnik M. B. , Altman C.
Published: July 2002

High rate sputtering of nickel using dc planar magnetron was successfully developed in East Fishkill for high throughput requirement. Rates in excess of 10 kA/min from targets up to 3/8 in. thick were achieved. Magnetic field strength was found to be the key parameter in depositing nickel at high rates, which has not been very successful in the coating industry. A minimal or sufficient magnetic field strength (mfs) about 300 G at Ni target surface is crucial in forming a stable plasma in dc magnetron sputtering. This minimal mfs can be generated with a strong magnet in the cathode assembly. Upon reaching this mfs, the I–V characteristics in Ni sputtering process follow the normal I=KVn relationship of dc planar magnetron sputtering. Nickel target thickness ranging from 1/8 to 3/8 in. with magnetic field strength ranging from 300 to 800 G were investigated in developing this process. The process can only be controlled well with a fine mfs adjustment. The sputtering equipment for magnetic material deposition must contain an adjustment mechanism in its cathode design in order to control mfs. Nickel film quality also seems to be affected by mfs due to the electron heating of the substrate and low angle incident atoms. A desired quality film of magnetic material such as Ni can be achieved with an optimal sputtering process that has a constant magnetic field strength at the target surface.
Exit loss in viscous tube flow
Authors: Santeler Donald J.
Published: July 2002

Numerous errors abound in the perception and calculation of gas flow in short tubes. This paper will develop modified equations for short-tube viscous flow in circular tubes with either a choked or a nonchoked exit. Several practical examples will be presented for vacuum component and system analysis. These equations and techniques are then combined with corresponding information from molecular flow studies to develop a new composite approach to gas flow in the transition range. The final result is a simplified approach to computer solutions of gas flow for orifices, short tubes, and long tubes—from molecular flow to atmospheric pressure.
Charge transport in magnetrons
Authors: Rossnagel S. M. , Kaufman H. R.
Published: July 2002

The current conduction processes in a magnetron sputtering diode have been the subject of discussion since the origination of the device. Several techniques have been used to study these conduction processes. Langmuir probe measurements of electron temperature, density, and plasma potential show clear evidence of a positive space-charge sheath. The magnitude of the E×B drift current, determined by measuring the magnetic field induced by the current, is suggestive of Bohm diffusion as the principle means for electron conduction. Sheath thickness measurements, made optically, show a strong functional dependence on the discharge voltage. When the sheath dependences are substituted into Child’s law, the current and voltage are found to follow the earlier, empirical current–voltage relation used with magnetrons: I=kVn. It appears that Bohm diffusion is the appropriate function to describe the impedance of the magnetron plasma, and that conduction across the sheath is space-charge limited. Gas density measurements indicate a significant reduction in the plasma region due to gas heating, which is the primary reason for the increase in voltage with power.
Laser annealing of copper and silicon thin films
Authors: Bloch J. , Zeiri Y.
Published: July 2002

Studies of transient and permanent surface structures formed on copper and silicon thin films (about 1000 Å thick) as a result of low-intensity Ar+ laser pulses are presented. Using Nomarski interferometric microscopy and backscattered light photography it was found that following the film melting a transient bubble is formed on the surface. The bubble size is comparable with the beam diameter and its height may exceed several microns. On solidification this bubble shrinks to a considerably lower permanent structure. A monochromatic light beam focused on these surface structures produces a characteristic backscattered pattern of dark rings superimposed on a bright circular patch. The dark rings are the result of interference between the beams reflected from the bubble external surface and the layer underneath. Transient bubbles can thus be observed using the interacting beam itself as a light source. Some examples of permanent and transient structures obtained under various beam parameters are presented.
A study of O2 and CO adsorption on thin evaporated chromium films
Authors: Thurner G. , Abermann R.
Published: July 2002

Internal stress measurements have been used to study oxygen and CO chemisorption and the oxidation of polycrystalline evaporated chromium films. The chemisorption of these gases on the chromium film gives rise to a compressive stress depending on the strength of the interaction between the metal and the respective gas. If the oxygen exposure of the chromium film exceeds 20 L a tensile stress superimposed on the compressive stress indicates the formation of a protective layer of chromium bulk oxide. The influence of the film structure as well as the film temperature during adsorption were investigated. The room-temperature adsorption behavior depends on the film deposition temperature up to about 150 °C but changes little at higher deposition temperatures. The temperature of adsorption has only a small effect on the compressive stress in the low-exposure regime but the subsequent tensile stress measured during the high oxygen exposure regime significantly increases with adsorption temperature. This is interpreted as indicating an increase in the thickness of the protective oxide layer formed.
Population and alignment of N2 scattered from Ag(111)
Authors: Sitz Greg O. , Kummel Andrew C. , Zare Richard N.
Published: July 2002

A well-characterized Ag(111) surface in an ultrahigh vacuum system is bombarded with supersonically cooled N2 and the scattered molecules are detected near the specular angle using 2+2 resonance enhanced multiphoton ionization. The first three even spatial moments of the angular momentum distribution have been measured. The zeroth moment is the population of a given rotational level, while the second and fourth moments describe the quadrupole and hexadecapole alignment of the J vector with respect to the surface normal. The relative population distribution shows an excess at high J characteristic of rotational rainbow scattering. For J>7, the second and fourth moments closely approach their limiting values expected when the J vector lies in the plane of the surface. It is concluded that the N2/Ag(111) system closely approaches the ideal of a rigid rotor colliding with a flat surface.
Studies of superconductors using a low-temperature, high-field scanning tunneling microscope
Authors: Kirtley J. R. , Feenstra R. M. , Fein A. P. , Raider S. I. , Gallagher W. J. , Sandstrom R. , Dinger T. , Shafer M. W. , Koch R. , Laibowitz R. , Bumble B.
Published: July 2002

We have developed a scanning tunneling microscope (STM) capable of operating at temperatures as low as 0.4 K and fields as high as 8 T. We have used this STM to study the energy gap of the high-Tc superconductors La–Sr–Cu–O and Y–Ba–Cu–O. We find that the reduced gap for these oxide superconductors falls in the range 3<2Δ/kBTc<7, for polycrystalline, single-crystal, and thin-film samples. We have also simultaneously imaged the surface topography and superconducting energy gap for thin films of the granular superconductor NbN. We occasionally see regions with smaller best-fit gaps that correlate with surface topographical features, but have been unable so far to image flux vortices.
Experimental tests of the steady-state model for oxygen reactive ion etching of silicon-containing polymers
Authors: Jurgensen C. W. , Shugard A. , Dudash N. , Reichmanis E. , Vasile M. J.
Published: July 2002

A steady-state model based on a silicon material balance has been proposed to predict the oxygen reactive-ion-etching resistance of organosilicon polymers. This model assumes that the rate determining step is sputtering of SiO2 film that forms on the surface of the organosilicon polymer. It predicts the etching rate of organosilicon polymers relative to the sputtering rate of SiO2 , based on the mass density of silicon in the polymer. The steady-state etching rate of a silyl novolac polymer is accurately predicted by the model over a wide range of etching conditions. Silyl methacrylates etch at the predicted rate under high-bombardment-energy conditions typical of trilevel processing, but exceed the predicted rate under low-bombardment-energy conditions. Surface analysis shows that the SiO2 film thickness continues to increase with time under these conditions, invalidating the steady-state approximation. Low silicon content (4.1 wt. %) polymers do not etch according to the model but form highly porous oxides that continuously accumulate on the surface of the polymer.
An evaluation of the composition of the residual atmosphere above a commercial dry pump
Authors: Wong W. , Laurenson L. , Livesey R. G. , Troup A. P.
Published: July 2002

In order to determine the degree of contamination in the residual atmosphere above a commercial pump having a swept volume free of oil, mass spectrometry techniques have been employed. It has been demonstrated that fluorocarbon levels are at least 1000 times lower than for conventional rotary vane pumps lubricated with perfluoropolyether. A detailed study of a four-stage, 80 m3 /h dry pump has been made to gauge the effect of various operating techniques involving gas ballast, interstage pumping, and operation in conjunction with mechanical booster pumps. The suitability of such oil-free pumps for clean pumping applications is demonstrated.
Glow discharge techniques for conditioning high-vacuum systems
Authors: Dylla H. F.
Published: July 2002

A review is given of glow discharge techniques which are useful for conditioning vacuum vessels for high-vacuum applications. Substantial development of glow discharge techniques has been done for the purpose of in situ conditioning of the large ultrahigh vacuum systems for particle accelerators and magnetic fusion devices. In these applications the glow discharge treatments remove impurities from vessel surfaces in order to minimize particle-induced desorption coefficients. Cleaning mechanisms involve a mixture of sputtering and ion(or neutral)-induced desorption effects depending on the gas mixture (Ar/O2 vs H2) and excitation method (dc, rf, and electron cyclotron resonance). The author will review the methodology of glow discharge conditioning, diagnostic measurements provided by residual gas and surface composition analysis, and applications to vessel conditioning and materials processing.