bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Integrity of a Standpipe Component in a Petrochemical Catalytic Cracking Unit: Part 2—Assessment of Embrittlement Effects
Authors: de O. Bueno Levi , Marino Luiz , Serra Flavio A. S. , Gazini Fernando T.
Published: July 2002

During a shutdown for general maintenance of a catalytic cracking unit, intergranular cracks were observed to occur during welding of the regenerator’s standpipe component manufactured from 2 1/4 Cr-1Mo steel. The cracking was observed to be related to intensive carbide precipitation in grain boundaries. To overcome the problem it was decided to heat-treat the relevant section of the component to dissolve these carbides and make possible its welding to a new virgin section of the tube. Samples of the material in its various conditions (virgin, ex-service, heat-treated, and welded) were taken to check the efficiency of the thermal treatment in reducing the embattlement effects and to carry out a general assessment of the remaining life of the component related to creep behavior considering notched bar creep specimens. [S0094-4289(00)00503-X]
Turbulence Attenuation by Small Particles in Simple Shear Flows
Authors: Graham David I.
Published: July 2002

This paper is concerned with the influence of a dispersed phase on carrier flow turbulence. The carrier flow is assumed to be a simple homogeneous shear, in which the fluid Reynolds stress tensor is independent of spatial location, but in which there is a linear mean shear across the flow. In the shear flow, the Reynolds stress is nondiagonal, and we find extra dissipation terms in the Reynolds stress equations compared with those arising in isotropic turbulence. The source terms are used to develop a simple model to predict changes in turbulence levels in particle-laden shear flows. It is shown that the general effect of particles is to attenuate turbulence. The resulting expression is not explicitly dependent on the shear. The theory is used to predict turbulence attenuation in near-homogeneous particle-laden flows in pipes and channels and is compared with experimental data. [S0098-2202(00)00401-6]
Fluid Dynamics and Transport of Droplets and Sprays
Authors: Sirignano, W. A. , Edwards, Chris F.
Published: July 2002

[S0098-2202(00)03201-6]
An Experimental Study of Electrohydrodynamic Induction Pumping of a
Stratified Liquid/Vapor Medium
Authors: Wawzyniak M. , Seyed-Yagoobi J. , Morrison G. L.
Published: July 2002

Electrohydrodynamic induction pumping of a stratified liquid/vapor medium is quantitatively assessed utilizing Laser Doppler Anemometry. Data are presented suggesting that pumping is due to both interfacial and bulk effects. Values of turbulence intensity associated with this type of flow are briefly discussed for the various cases studied. [S0022-1481(00)00401-1]
Stiffness and Damping in Mechanical Design
Authors: Rivin, Eugene I. , Balachandran, B.
Published: July 2002

[S1050-0472(00)01501-4]
Analysis of Squeeze Film Dampers Operating With Bubbly Lubricants
Authors: Tao Luoyi , Diaz Sergio , Andre´s Luis San , Rajagopal K. R.
Published: July 2002

Rotor-bearing systems supported on squeeze film dampers (SFDs) show large amplitude vibratory motions when traversing critical speeds. At these operating conditions air is drawn into the damper thin film clearance generating a bubbly mixture with the lubricant and producing SFD forces not readily predictable with currently available analysis. A continuum model is proposed for describing the motion of a bubbly fluid in an open ended SFD operating with circular centered journal orbits. Computed predictions for peak-peak dynamic pressures and fluid film forces agree reasonably well with experimental measurements conducted on a SFD test rig operating with a controlled air in oil mixture. The bubbly flow model provides an initial procedure towards the reliable design of SFDs in actual operating conditions. [S0742-4787(00)02601-1]
Mechanism for Subambient Interfacial Pressures While Polishing With Liquids
Authors: Levert Joseph A. , Danyluk Steven , Tichy John
Published: July 2002

This paper reports the results of a model for predicting the development of subambient pressures during the polishing of flat hard substrates by sliding against a compliant pad in the presence of a slurry (liquid). This work is an extension of our prior experimental work on the polishing of single crystal silicon wafers with polyurethane pads and high pH slurries containing silica particles. Subambient pressures have important implications in the polishing rate and uniformity of silicon and, therefore, in the manufacture of large-scale integrated circuits. The subambient pressure is the result of pad asperity compression at the wafer leading edge followed by elastic reexpansion beneath the wafer due to the nonuniform wafer/pad contact stress. Liquid is expelled from interasperity voids where high leading edge contact stress causes asperities to be compressed. Lower contact stress behind the leading edge causes asperity reexpansion leading to recreation of interasperity voids and subambient liquid pressures. A Poiseuille like in-flow of liquid from the sides of the wafer limits the value of the subambient pressure. Numerical simulations predict subambient pressures as a function of liquid viscosity and relative velocity of the pad and wafer and the pad and wafer mechanics which follow the same trend as the experimental data. [S0742-4787(00)01702-1]
Characterization of Polystyrene (1 kDa) with a Perfluorinated Endgroup by TOF-SIMS: Effects of Sample Preparation
Authors: Belu A. M. , Hunt M. O. , Linton R. W.
Published: July 2002

TOF-SIMS measurements of a thick film 1 kDa polystyrene functionalized with a perfluoroalkyl endgroup are presented. Characteristic fragment signals in the low mass range are observed. The thick film of 1 kDa functionalized polystyrene is also analyzed with an overlayer of silver. This modification in sample preparation allows intact oligomer signals to be generated from the surfaces of thick films (i.e., in bulk form) of low molecular weight polymers.
Nickel precipitation at nanocavities in separation by implantation of oxygen
Authors: Zhang Miao , Zeng Xuchu , Chu Paul K. , Scholz R. , Lin Chenglu
Published: July 2002

The structures of nickel decorated cavities and Ni precipitates epitaxially grown in the nanocavity band in separation by implantation of oxygen (SIMOX) are studied. The nanocavities are generated in the silicon substrate of the SIMOX wafer by proton implantation followed by Ni implantation into the Si overlayer. Channeling Rutherford backscattering spectrometry results indicate that Ni implantation changes the crystalline Si overlayer into amorphous Si. After annealing at 1000 °C for 2 h, the amorphous Si evolves into a polycrystalline structure composed of NiSi2 and polycrystalline silicon. In the meantime, most of the nickel atoms diffuse through the buried oxide layer and are gettered by the nanocavity band. NiSi2 precipitates are observed both in the nanocavities and at the residual defects created by H implantation. The microstructure of the Ni precipitate depends on whether there are cavities nearby. Without cavities in the vicinity, dislocations are observed in the neighborhood of the precipitate, whereas no dislocation is detected around the precipitate when there are nanocavities in the neighborhood. The precipitation and gettering behavior can be explained by the gettering of Si interstitials to the microcavities and lowering of the nucleation barrier.
Studies on Ru of [Ru(acac)3], [Ru(acac)2(CH3CN)2], [Ru(acac)2(topd-O,S], and [Ru(acac)2(μ-topd-O,S,O′)] (acac = acetylacetonato and topd = 3-thioxo-2,4-pentanedione) by XPS
Authors: Tanaka Kunihito , Endo Akira , Hashimoto Takeshi , Shimizu Kunio
Published: July 2002

The XPS of the novel sulfur-bridged binuclear β-diketonatoruthenium complexes of [Ru(acac)2(μ-topd-O,S,O′)] (acac = acetylacetonato and topd = 3-thioxo-2,4-pentanedione) and a monomeric ruthenium complex of [Ru(acac)2(topd-O,S)] were measured in order to obtain the information for the valence of the ruthenium, together with those of [RuII(acac)2(CH3CN)2] and [RuIII(acac)3] as the reference compounds of RuII and RuIII, respectively. The Ru 3d5/2 binding energy of [Ru(acac)2(topd-O,S)] (282.4 eV) is almost the same as that found for [RuIII(acac)3] (282.8 eV). Such an energy value is an indication of the presence of RuIII. However, the binding energy of Ru 3d5/2 for binuclear complex is 282.2 eV which is intermediate between RuII and RuIII found in [RuII(acac)2(CH3CN)2] (281.3 eV) and [RuIII(acac)3]. This means that the binuclear complex contains both RuII and RuIII and there could be some kind of delocalization of electron between the two ruthenium atoms via topd ligand. Alternatively, this can be described as a valence-averaged mixed-valent RuII and RuIII.
ZnO/GaN heterointerfaces and ZnO films grown by plasma-assisted molecular beam epitaxy on (0001) GaN/Al2O3
Authors: Hong S. K. , Ko H. J. , Chen Y. , Hanada T. , Yao T.
Published: July 2002

We report the structures of ZnO/GaN heterointerfaces and properties of ZnO films grown by plasma-assisted molecular beam epitaxy (P-MBE) on (0001) GaN/Al2O3 substrates. At first, different preparations (zinc or oxygen-plasma pre-exposures) of the GaN surface are examined and the resultant heterointerface structures and properties of ZnO films are studied. The oxygen-plasma pre-exposure of the GaN surface results in the formation of an interface layer, while the formation of interface layers is prevented by zinc pre-exposure. The interface layer is identified as single-crystalline monoclinic Ga2O3 through extensive transmission electron microscopy (TEM) study. The orientation relationship between monoclinic Ga2O3 of the interface layer and GaN and ZnO epilayers is investigated as (0001) GaN∥(001) Ga2O3∥(0001) ZnO and [2-1-10] GaN∥[010] Ga2O3∥[2-1-10] ZnO. Based on structural investigations and stability of bondings, we propose interface-bonding sequences at the ZnO/GaN heterointerfaces in zinc or oxygen-plasma pre-exposed samples: “N–Ga–O–Zn” bonding sequence for zinc pre-exposed samples and “N–Ga–(O-terminated Ga2O3 layer)–Zn–O” for oxygen-plasma pre-exposed ones. Lattice misfit of Ga2O3 against underlying GaN (against upper ZnO) is estimated as −4.7% (−6.5%) and 10.7% (8.6%) along the [010] and [100] directions of the Ga2O3, respectively. The structural and optical properties of ZnO films evaluated by TEM, high-resolution x-ray diffraction and photoluminescence spectroscopy consistently reveal better crystal quality of zinc pre-exposed ZnO films than oxygen-plasma pre-exposed ones. Second, the effects of high temperature annealing on ZnO films grown at low temperature on zinc pre-exposed GaN surface are studied. Surface morphology is dramatically changed by high temperature annealing; three-dimensional island morphology on as-grown ZnO layers changes into atomically flat morphology with atomic level steps and terraces through high temperature annealing. Optical properties are also improved by high temperature annealing: (i) The intensity of band edge emissions from the ZnO films increases with their full width at half maximum values being decreased. (ii) Free exciton emission from annealed films is considerably enhanced in intensity compared to as grown films. These results indicate that high temperature annealing greatly improve the crystal quality of ZnO films grown at low temperature.
Microwave plasma nitriding of a low-alloy steel
Authors: Hovorka D. , Vlček J. , Čerstvý R. , Musil J. , Bělský P. , Růžička M. , Han Jeon G.
Published: July 2002

A low-alloy steel was nitrided in the downstream zone of an electron cyclotron resonance (ECR) discharge at low pressure (0.15–0.25 Pa). Structure and properties of the nitrided surfaces were primarily controlled by the substrate temperature Ts (300–550 °C), the nitrogen–hydrogen–argon gas mixture composition, and the substrate bias voltage Ub (−1000 to +40 V) at a typical value of the incident microwave power Pi=900 W, the distance of the substrate from output aperture of the ECR source was d=250 mm, and the nitriding time t=2 h. Optical emission spectroscopy was used to study the behavior of significant atomic and molecular species, such as N2, N2+, NH, H, Fe, Ar, and Ar+, in front of the nitrided sample. It has been found that due to a high plasma reactivity, nitriding is effective at substrate temperatures Ts⩾500 °C, when the surface hardness is about 1200 HV0.05 and a diffusion layer thickness up to 120 μm has been achieved for t=2 h. The presence of 10%–30% H2 in a nitrogen–hydrogen gas mixture enhances the efficiency of nitriding in comparison with treatment in pure nitrogen under the same conditions. For Ts⩾500 °C, the process is effective even for substrates at positive potential (Ub=+30 V) and for a lower amount of N2 (10%–30%) in a nitrogen–hydrogen–argon gas mixture, for which no compound layer is formed on the nitrided surface. However, the negative substrate bias voltage Ub enhances considerably the efficiency of nitriding only at lower substrate temperatures (Ts≈400 °C), when the nitriding is relatively weak.
Effect of hydrogen dilution on the structure of SiOF films prepared by remote plasma enhanced chemical vapor deposition from SiF4-based plasmas
Authors: Alonso J. C. , Pichardo E. , Pankov V. , Ortiz A.
Published: July 2002

Structural and electrical properties of fluorinated silicon dioxide (SiOF) films prepared by remote plasma enhanced chemical vapor deposition from the SiF4–O2–H2–He gas mixture have been studied using ellipsometry, Fourier transform infrared spectroscopy, transmission electron microscopy, and current–voltage measurements. It has been found that the level of hydrogen dilution strongly affects the microstructure of deposited SiOF films. The films prepared at the H2 flow rate below about 0.8 sccm have a biphase structure consisting of an amorphous matrix with the incorporation of 5–30 nm sized particles. The main origin of these particles seems to be gas phase oxidation of SiFx species (with x=1, 2, 3) in plasma and downstream regions. Resulting films are characterized by extremely low density, reduced structural homogeneity, and poor electrical properties. Increase in the H2 flow rate above 0.8 sccm completely suppresses the incorporation of particles into the growing film probably due to effective hindering gas phase oxidation process and results in dense homogeneous amorphous SiOF films with good electrical properties.
Electron population above 13.5 eV in ultrahigh frequency and inductively coupled plasmas through C2F4/CF3I and C4F8/Ar gas mixtures
Authors: Nakano Toshiki , Samukawa Seiji
Published: July 2002

Electron population above 13.5 eV in the plasma through the C2F4/CF3I mixture, which is novel chemistry proposed for low-damaged, fine structure etching of SiO2, is studied by Ar emission analysis and Langmuir probe measurement. The integrated electron energy distribution function (eedf) above threshold energy for Ar 750.4 nm emission (13.5 eV) exhibits the weaker dependence on the gas composition for the C2F4/CF3I mixture than for the C4F8/Ar mixture which is conventional chemistry for SiO2 etching. In the practical etching conditions, the integrated eedf above 13.5 eV for the C2F4/CF3I mixture becomes smaller than one third of that for the C4F8/Ar mixture, regardless of the plasma sources used in this study (ultrahigh-frequency plasma and inductively coupled plasma sources). These results indicate that even lower charging damage of devices would be expected in SiO2 etching using the C2F4/CF3I chemistry than the C4F8/Ar chemistry.
Experimental and Statistical Investigations on the Measurement of Very Low Ion Currents in Mass Spectrometers
Authors: Blauth E. W. , Draeger W. M. , Kirschner J. , Liebl H. , Müller N. , Taglauer E.
Published: July 2002

Ion-electron converters with low background current have been applied for the investigation of residual gas mass spectra. From the abundance distribution of the secondary electrons, measured with scintillation and surface barrier detectors, counting losses can be determined for different ion masses. Ion currents as low as some 10−22 A are measurable. The corresponding error limits are considered by a statistical analysis including the background current. Criteria are given to distinguish a mass peak from the background within a definite error probability.
Macroscopic particle motion in quadrupole fields
Authors: Whetten N. Rey
Published: July 2002

The motion of ions in quadrupole field spectrometers was simulated using large particles (10–40 μ diam) that can be visually observed, with appropriate scaling of the voltage and frequency parameters. In air, the motion of the large particles is damped by the viscous medium, but their stability properties are still governed by the Mathieu equation. A new method is suggested for pulsing ions out of the 3-dimensional quadrupole mass spectrometer.
rf Sputtered Luminescent Rare-Earth Oxysulfide Films
Authors: Maple T. G. , Buchanan R. A.
Published: July 2002

Thin luminescent films of lanthanum and gadolinium oxysulfide (RE2O2S) were prepared by radio-frequency sputtering in an Ar–H2S mixture. Small additions of Eu, Tb, or Tm produced red, green, or blue emissions, respectively. A luminance of 40 000 ftL from a La2O2S:Tb film was observed. The composition of the sputtered films was found to be very dependent upon the H2S pressure in the sputtering chamber. The film composition as a function of H2S pressure was determined and described. In order to achieve maximum luminescence, the films were treated in an H2–SO2 atmosphere at 1000 °C, and x-ray diffraction and luminous emission linewidths were observed to have decreased after treatment. Crystalline growth within the film and improved oxygen sulfur stoichiometry resulting from the treatment process are believed to be primarily responsible for the increase in luminous efficiency. The maximum luminous efficiency of the films was measured to be approximately 1/10 that of corresponding powder screens. Attempts to increase the film luminance by reducing the internal trapping of the radiation are discussed.
Kinetics of Thermal Decomposition of TiH2
Authors: Schoenfelder C. W. , Swisher J. H.
Published: July 2002

The thermal decomposition rate of TiH2 over the temperature range 250–500 °C (523–773 K) in a continuously pumped vacuum system was found to be much slower than predicted from diffusion model calculations. The rate was insensitive to the presence of oxygen in the environment and on the specimen surface; however, small amounts of residual hydrogen in the chamber decreased the rate considerably. The rate controlling process appears to be the reaction between hydrogen atoms to form gaseous molecules on the surface. When specimens were decomposed in flowing helium, the rate was slower than in vacuum, indicating that diffusion of hydrogen through a gaseous boundary layer on the surface can control the rate when a second gas is present.
Surface profile measurements — a survey of applications in the area of vacuum deposition
Authors: Breitweiser G.
Published: July 2002

A brief discussion of stylus profile measurement techniques is presented followed by illustrations of the application of stylus methods to film deposition measurement problems. Suggestions are presented for reducing errors and improving measurement accuracy. The effect of stylus shape and size on profile resolution is discussed, as well as deformation of specimen films due to stylus contact. Results of measurements of films in the 100-Å range are presented. Among the variety of applications of profile measurements illustrated are substrate flatness and texture, pattern registration, penumbra evaluation, and specially contoured films such as vacuum deposited lenticulars. Several of the illustrated profiles are correlated with scanning electron micrographs.
Improved thermogravimetric magnetic susceptibility apparatus
Authors: Lewis R. T.
Published: July 2002

An apparatus incorporating a vacuum microbalance that can make simultaneous measurements of both the mass of a sample and its magnetic susceptibility is described. The Faraday technique is employed to measure the susceptibility, but the field gradient is provided by a set of coils rather than the shaped pole faces commonly used. Because the gradient can be reversed in less than one second, by switching the coil current, the susceptibility can be measured even when sample mass is changing rapidly. This allows one to correlate changes in susceptibility with mass during in situ chemical reactions. The system also includes a variable temperature probe that can vary sample temperature in a controlled manner through the range of 4.2 K to over 800 K in a few minutes. Measurements made during the sulfiding of a CoO-MoO3-Al2O3 catalyst are presented as an example of the use of the apparatus.
Effect of various sputtering parameters on Ta phase formation using an I-Optimal experimental design
Authors: Whitman Charles S.
Published: July 2002

Five process factors are varied to find conditions necessary for α and β phase formation in tantalum thin films deposited on SiC. These are: sputtering time, input power, presputter etch time, preheat time at 250 °C, and sputtering temperature. An empirical model is developed that predicts the maximum or minimum amount of β phase possible over a large range of film thickness (∼25–∼2000 nm). The maximum predicted (average) percent β phase at the maximum sputtering temperature is only 8%, with 95% confidence bounds of [3%, 17%]. The other factors place a much lower restriction on β phase formation. Pure α phase is easily produced over a wide range of operating conditions. Only a weak relationship is found between film thickness and phase composition. The Ta film resistivity increases with the amount of β phase, in agreement with the literature.
High-purity, ultrahigh-resolution calixarene electron-beam negative resist
Authors: Manako Shoko , Ochiai Yukinori , Yamamoto Hiromasa , Teshima Takahiro , Fujita Jun-ichi , Nomura Eiichi
Published: July 2002

Calixarene is a promising high-resolution negative electron-beam resist having a resolution of the order of 10 nm because of its low molecular weight. We have made a purified calixarene resist containing metal contaminants whose concentrations are measured in parts per billion and which therefore do not degrade the performance of silicon-based electron devices. The purity of the calixarene itself was also improved and we obtained high-purity calix[6]arene and high-purity calix[7]arene, both of which contain the main component, which is more than 95% of all the calixarene present. The resolution of both purified calixarene resists is almost the same as that of the unpurified calixarene, but the sensitivity of calix[7]arene is higher than that of calix[6]arene because its molecular weight is higher.
True and measured outgassing rates of a vacuum chamber with a reversibly adsorbed phase
Authors: Akaishi K. , Nakasuga M. , Funato Y.
Published: July 2002

The modeling for the pumpdown of a vacuum chamber with a reversibly adsorbed phase is carried out and the outgassing equation which predicts variations of surface coverage and gas density with time is derived. When it is assumed that the wall surface of a vacuum chamber consists of oxide layer and this layer involves weakly chemisorbed (nondissociate) H2O with desorption energies from 20 to 30 kcal/mol, it is shown that the calculated outgassing rate from the outgassing equation well explains the experimental result that the outgassing rate measured by the orifice pumping method in the unbaked stainless steel chamber is dependent on pumping speed.
Grid lens approach for high effective emittance in SCALPEL®
Authors: Moonen D. , van Kranen S. , Kruit P. , Katsap V. , Waskiewicz W. K.
Published: July 2002

The emittance required for the SCALPEL system is very large; on the order of 2 mm mrad. This can be achieved with an electron source using advanced, large area cathodes and complicated extraction optics, but in this article an alternative approach is presented: devices which increase the effective emittance of an electron beam by creating an array of subbeams. After we have explained the theory, we discuss three different configurations which form electrostatic microlens array-like fields, and we show results from computer modeling.
Effects of a two-step rapid thermal annealing process on Mg-doped p-type GaN films grown by metalorganic chemical vapor deposition
Authors: Ahn Kwang-Soon , Kim Dong-Joon , Moon Yong-Tae , Kim Hyo-Gun , Park Seong-Ju
Published: July 2002

A two-step rapid thermal annealing (RTA) process is proposed in order to improve the electrical properties, the crystal quality, and the surface roughness of Mg-doped p-type GaN films. In the two-step RTA process, the first low temperature step (600 °C) with a long annealing time (5 min) was followed by the second high temperature (950 °C) step with a short annealing time. These results show that the two-step RTA process significantly improves electrical properties and reduces the surface roughness of p-GaN compared to the one-step RTA process.
Growth of well-aligned carbon nanotubes on nickel by hot-filament-assisted dc plasma chemical vapor deposition in a CH4/H2 plasma
Authors: Hayashi Yasuaki , Negishi Tetsu , Nishino Shigehiro
Published: July 2002

Well-aligned carbon nanotubes were grown perpendicular to the surface of Ni substrates by hot-filament-assisted dc plasma chemical vapor deposition in a CH4/H2 plasma. It was found, from observation by a scanning electron microscope and a transmission electron microscope, that the nanotubes starting from the side grew first parallel to the plasma boundary and then toward the plasma while those starting on the surface facing the plasma grew straight toward it. It has been suggested that force toward the plasma caused by the local electric field in the sheath and negative charge at the top of nanotubes assist them to grow well-aligned and perpendicular to a substrate in a dc discharge.
Ferromagnetic resonance of monodisperse Co particles
Authors: Wiedwald U. , Spasova M. , Farle M. , Hilgendorff M. , Giersig M.
Published: July 2002

Two-dimensional arrays of monodisperse nanosized Co particles are prepared on carbon and glass substrates by a magnetophoretic deposition technique from colloidal suspensions. Transmission electron microscopy (TEM) reveals a complicated cubic crystalline structure of the particles and hexagonal ordering over several micrometers squared, if the colloidal suspension is dried in magnetic fields of up to 0.8 T. Angular-dependent ferromagnetic resonance (FMR) spectra of 4-, 5-, 9-, and 12-nm-diameter particles at 297 K show that the easy axis of magnetization is in plane and that only the 12 nm particles are measured below the blocking temperature estimated to be 656 K. The resonance linewidth is on the order of 0.1 T, indicating a much larger magnetic inhomogeneity of the particles than the small geometric and size distribution (<10%) observed by TEM suggests. Characteristic differences of the FMR spectra for different substrates and deposition parameters are observed.
Analysis of injection current through thin gate oxide during metal etch
Authors: Kinoshita Takashi , Krishnan Srikanth , Dostalik Willam W. , McVittie James. P.
Published: July 2002

A charging damage mode due to “latent antenna” formation for high aspect ratio structures in a metal etch process was investigated by a new surface charging simulation technique. The latent antenna is formed at the end of the metal etch process because of the microloading effect, and is connected to a transistor gate with 35 Å thickness. By using a new simulation algorithm, the plasma stress current current–voltage (I–V) characteristic caused by topography dependent charging was calculated for different ranges of the injection current to the antenna structure. Subsequent gate injection current through the thin gate oxide was estimated by the plasma I–V with a measured holding current I–V characteristic especially optimized for high current injection. The plasma I–V was calculated for the latent antenna and a mask-defined structure (overetch structure), which are formed during an overetch period. The steady state gate injection current is largest during the latent antenna formation. Because of a device degradation characteristic that is mostly controlled by an initial gate injection charge, the high injection current for the latent antenna defines the degree of damage, and the observed degradation independence of the overetch time is well explained by the results. Since the initial gate injection charge depends on the period of latent antenna formation, damage increases as the etching rate decreases at the narrow space region. The injection current gets smaller with a smaller antenna ratio, and antenna structures without high aspect from the gate injection current. For the analysis of thin gate oxide degradation, the injection current is more important than the charging voltage.
Study of ZrO2 thin films for gate oxide applications
Authors: Nam Seok-Woo , Yoo Jung-Ho , Kim Hae-Young , Kang Sung-Kwan , Ko Dae-Hong , Yang Cheol-Woong , Lee Hoo-Jeong , Cho Mann-Ho , Ku Ja-Hum
Published: July 2002

We investigated the microstructures and electrical properties of ZrO2 films deposited by reactive dc magnetron sputtering on Si substrates for gate dielectrics applications. We observed that the refractive index value of the ZrO2 films increased with an increase in deposition powers and annealing temperatures. The ZrO2 films deposited at elevated temperatures are polycrystalline, and both the monoclinic and tetragonal phases exist in the films. Films with higher density and improved crystallinity are obtained at higher deposition temperatures. The interfacial oxide layer between ZrO2 films and Si substrates grew upon annealing in the O2 gas ambient, which is due to the oxidation of Si substrates by the diffusion of oxidizing species from O2 gas ambient. The accumulation capacitance value increased upon annealing in the N2 gas ambient due to the densification of the films, while it decreased in O2 gas ambient due to the growth of the interfacial oxide layer.
Scanning tunneling spectroscopy of field-induced Au nanodots on ultrathin oxides on Si(100)
Authors: Park Jeong Young , Phaneuf R. J. , Williams E. D.
Published: July 2002

We present tunneling spectra for nanometer scale Au dots on in situ oxidized Si(100). The spectra were measured for dots fabricated on clean and oxidized surfaces for oxide thickness from 0 to 1 ML. Two important features are observed. First, tunneling current–voltage spectra of the dots on the atomically clean surfaces show metallic behavior, confirming the identification of the dots as deposited Au from the tip. Second, tunneling spectra from Au dots on the partially oxidized surfaces show a feature at approximately 2 V (sample positive) with weak negative differential resistance. We associate this feature with oxide related defect sites which we observe at densities that increase from 0.06 to 0.3/nm2 as oxide coverage increases from 0.1 to 1 ML. The probability of observing this feature through a gold dot increases by about a factor of 2, suggesting that the dot increases the effective sampling area of the defect sites by the same factor.
Surface characterization of oxidative corrosion of U–Nb alloys
Authors: Kelly Dan , Lillard Jennifer A. , Manner William L. , Hanrahan Robert , Paffett Mark T.
Published: July 2002

We have studied the relative rates of oxidative corrosion of U–Nb alloys containing 2–8 wt. % Nb, using x-ray photoelectron spectroscopy and depth profiling by sputtered neutrals mass spectroscopy. The alloys have been characterized after exposure to dry and humidified air (up to 50% relative humidity) at temperatures from 25 to 125 °C, and after exposure to electrochemical solutions. Oxidation of the U–Nb alloys in a tube furnace results in oxide layers comprised of UO2 and Nb2O5 under all experimental conditions used. The thickness of the oxides increased with treatment time and temperature, but decreased with increasing Nb alloy content. For example, a 48 h treatment at 75 °C and 50% relative humidity results in an oxide layer on U–2% Nb that is approximately 1.5 times as thick as that on U–8% Nb. Electrochemical oxidation of U–Nb alloys facilely generated UO3(⋅nH2O) and Nb2O5 layers ∼1000 Å thick, qualitatively similar to thermal oxidation results. U–Nb alloys electrochemically oxidized at low pH exhibit oxide layers with near-surface regions (50 Å) enhanced in Nb content, as compared to the bulk material. Surface UO3(⋅nH2O) was not readily reduced upon exposure to molecular D2; however, D atoms facilely reduced UO3(⋅nH2O) to UO2.
Study of the early stage of SiO2 growth by a TEOS–O2 plasma mixture using a three-dimensional Monte Carlo model
Authors: Rhallabi A. , Turban G.
Published: July 2002

Three-dimensional kinetic Monte Carlo calculations have been carried out to study the film growth of SiO2 by a TEOS–O2 plasma mixture. The kinetic surface mechanisms take into account the nucleation phase process, the physisorption of reactive TEOS fragments, and the migration process. The main process contributing to the SiO2 growth is the formation of the oxygen bridge between two surface silicon sites. The simulations show the role of the substrate energy and the percentage of the nucleation center on the nucleation phase evolution. Good adhesion is obtained for a high surface energy of the substrate. A high surface energy increases the mobility of the reactive species on the surface substrate by the reduction of the desorption process in the early stage. On the other hand, the increase of the oxidation probability leads to the decrease of the mobility of physisorbed species on the film surface and, consequently, to increased root-mean-square roughness of the deposited film.
Optical properties of oxygen-ion-implanted benzocyclobutene films
Authors: Mada Yoichi , Sugitani Suehiro , Arai Kunihiro , Yamasaki Kimiyoshi
Published: July 2002

Alteration of the refractive index of benzocyclobutene film by oxygen-ion implantation has been investigated. An increase in the refractive index of 3.8% was observed with an oxygen ion dose of 3×1014 cm−2. The optical loss of the ion-implanted region was measured using both surface planar waveguides and channel ones. With the latter structure, a 2.3 dB/cm propagation loss was obtained with an oxygen-ion dose of 1014 cm−2. The refractive index increase and the optical loss were stable against heat treatments. It was deduced that the refractive-index increase can be attributed to compression of the film and additionally to oxidation of the film.
Selective chemical vapor deposition of copper on AZ 5214™-patterned silicon substrates
Authors: Davazoglou D. , Vidal S. , Gleizes A.
Published: July 2002

Copper features with dimensions down to 0.5 μm were fabricated on silicon substrates by selective chemical vapor deposition. For the fabrication, oxidized (100) silicon substrates were used, covered with a film grown by low-pressure chemical vapor deposition at 0.1 Torr and 550 °C, from W(CO)6 decomposition. These substrates were subsequently covered with AZ 5214™ photosensitive polymer, which has been developed as both positive and negative tone resist. Copper was then chemically vapor deposited on the patterned substrates by 1, 5-cyclooctadiene Cu(I) hexafluoroacetylacetonate decomposition, at 1 Torr and temperatures of 110 and 140 °C. A vertical, cold-wall reactor was used, equipped with an UV lamp permitting photon-assisted deposition. Under UV illumination, copper was deposited on resist covered and uncovered parts of the substrate. In the absence of illumination, the metal was selectively grown on the tungsten film only at relatively slow rates (1 and 3.5 nm/min at 110 and 140 °C, respectively). Copper films had a granular form with a grain size increasing with temperature (150 and 550 nm at 110 and 140 °C, respectively). After depositions, the resist was removed in oxygen plasma leading to the formation of fine copper features.
Formation of metallic surface structures by ion etching using a S-layer template
Authors: Panhorst M. , Brückl H. , Kiefer B. , Reiss G. , Santarius U. , Guckenberger R.
Published: July 2002

Crystalline cell surface layers (S-layer) of the bacteria species Deinococcus Radiodurans are used as a nanometric template for patterning thin ferromagnetic films. A hexagonal pattern of uniform 10-nm-wide dots and a lattice constant of 18 nm is fabricated from 2.5-nm-thick sputter deposited Co, FeCo, Fe, CoNi, and NiFe. Suitable parameters for the subsequent Ar ion etching are elaborated. For successful patterning, the etching energy ranges from 50 to 300 eV and the etching time from 17 to 283 s at an ion current of 1.5–5.5 μA/cm2. The formation of nanodot arrays is demonstrated by scanning electron and scanning force microscopy.
In situ analysis of perfluoro compounds in semiconductor process exhaust: Use of Li+ ion-attachment mass spectrometry
Authors: Nakamura M. , Hino K. , Sasaki T. , Shiokawa Y. , Fujii T.
Published: July 2002

Ion-attachment mass spectrometry is capable of accurate and in situ analysis of multicomponent gases that may even include unknown components. We developed a compact apparatus that uses this method and examined its performance for perfluoro compounds, a class of greenhouse gases, using typical standard gases, and subsequently applied the method to the in situ analysis of exhaust gases from a dry-etching machine, where c-C4F8/O2/Ar plasma is generated. Perfluoro compounds of low concentration can be detected as quasimolecules without any fragmentation. In the exhaust gases, many components that are not considered in the current measurement protocol [J. Meyers, D. Green, P. Maroulis, and W. Reagen, Equipment Environmental Characterization Guidelines, Rev. 3.0 (INTEL, 1999)] are measured, as well as components already reported.
Effect of annealing ambient on WSix(x=2.3) sidewall deformation and contact resistance in dichlorosilane-based W-polycide gate
Authors: Park Sang-Wook , Kim Dong-Jin , Dong Cha-Deok , Kwak Noh-Yeal , Kong Young-Taek , Lee Chan-Ho , Lee Seung-Cheol , Park Se-Ho
Published: July 2002

To analyze the deformation of the WSix sidewall in a W-polycide gate, WSix(x=2.3) film was deposited by a modified dichlorosilane (SiH2Cl2, DCS) process that consisted of in situ monosilane (SiH4, MS)-based WSix nucleation, followed by DCS-based WSix deposition at 550 °C. Compared to the conventional DCS-based WSix film, the WSix film did not exhibit a W-rich interface facilitating the deformation and it showed similar structural property. Examination of deformation dependence on heat-treatment ambients suggested that a deformed region having a detrimental morphology was formed at the WSix sidewall during both nonoxidizing and oxidizing ambient annealings. It was revealed that the deformation in nonoxidizing and oxidizing ambient annealing resulted from the formation of a Si precipitate and W–Si–O compound at the WSix sidewall, respectively. In the case of N2 ambient preannealing at 600 °C for 30 min in the process of spacer oxide deposition, the deformation could be effectively suppressed by preventing the formation of Si precipitate at the WSix sidewall. The N2 ambient preannealing also improved the contact resistance of metal (Al/W plug with TiN/Ti barrier) on the W-polycide gate by promoting silicidation between Ti and excess Si in the WSix layer.
Molecular-beam-epitaxy growth and luminescence properties of Nd3+-doped LaF3/CaF2 thin films
Authors: Zhang X. , Daran E. , Lahoz F. , Serrano C. , Pita K. , Lam Y. L.
Published: July 2002

Nd 3+ -doped LaF3 heteroepitaxial waveguide films on two oriented CaF2 substrates were grown by the molecular-beam-epitaxy method. The spectroscopic properties of Nd3+ in the epitaxial films have been studied by using a tunable Ti:sapphire laser. Efficient IR emissions have been detected at 1.06, 0.86, and 1.32 nm ranges. The influences of substrate orientation, Nd3+ concentration, and temperature on the luminescence properties were investigated. By using a prism-coupling technique, waveguided luminescence has been measured at room temperature. Furthermore, laser emission at 1.06 μm was obtained at room temperature with a 790 nm laser pump.
Molecular-beam study of the plasma-surface kinetics of silicon dioxide and photoresist etching with chlorine
Authors: Chang Jane P. , Sawin Herbert H.
Published: July 2002

The plasma-surface kinetics of silicon dioxide and photoresist etching in chlorine were measured by beam scattering in which the Ar+, Cl, and Cl2 beams were independently controlled at fluxes comparable to a high-density plasma etching process. The etching was characterized as a function of Ar+ ion energy, ion flux, chlorine-to-ion flux ratio, and the ion impingement angle. Molecular chlorine did not enhance the etching of silicon dioxide, but atomic chlorine enhanced the etching of oxide by a factor of 4 at flux ratios around 100. The ion energy dependence for oxide was a linear function of (Eion1/2−Eth1/2), where the threshold energy Eth was found to be approximately 40 eV. The oxide angular dependence showed a maximum etching yield at ∼60° off-normal ion incident angle, indicating that physical sputtering is the rate limiting mechanism. Angular resolved x-ray photoelectron spectroscopy analysis suggests that ion bombardment sputters oxygen and allows atomic chlorine to bond to silicon. The etching of chlorinated silicon is assumed to be enhanced by subsequent ion bombardment in a manner similar to ion enhanced polysilicon etching with chlorine. The angular dependence of photoresist etching exhibited a maximum at ∼60° off-normal ion incident angle, indicating that sputtering is the important etching mechanism.
Pattern transfer from a biomolecular nanomask to a substrate via an intermediate transfer layer
Authors: Winningham Thomas A. , Whipple Steven G. , Douglas Kenneth
Published: July 2002

We have achieved pattern transfer from a biomolecular nanomask (bionanomask) to a crystalline Si substrate using inductively coupled plasma etching. This nanopatterning makes use of an intermediate transfer layer (ITL) between the masks and the substrate. The ITL is a layer of a resist-like material into which the bionanomask pattern is transferred before it is then transferred to the substrate. We report a method for using bionanomasks deployed on an ITL of ultrathin (<10 nm) nitrocellulose to pattern a Si(100) substrate with either a two-dimensionally ordered array of 10-nm-diam holes or alternatively a two-dimensionally ordered array of 10-nm-diam metal dots. Both arrays possess hexagonal symmetry and a lattice constant of 22 nm. In the case of nanodot array fabrication, the ITL thus facilitates the direct replication of the inverse pattern of the bionanomask in the form of ordered metal nanodots without the need for adsorbate surface diffusion and nucleation steps.
Crystallization kinetics in amorphous (Zr0.62Al0.38)O1.8 thin films
Authors: van Dover R. B. , Lang D. V. , Green M. L. , Manchanda L.
Published: July 2002

Thin films of Zr0.62Al0.38O1.8 are amorphous when deposited at room temperature by rf magnetron sputtering. Crystallization occurs during subsequent annealing in the temperature range of 700–1000 °C for times in the range of 10 s–100 h. The crystallite size and the fraction of the sample that had crystallized were determined using x-ray diffraction. The films were found to initially develop a low density of fairly large (∼8 nm) crystallites, while subsequent heat treatment was found to increase the density rather than the size of the crystallites. Crystallization can be described with a first-order rate equation; the rate constant is exponential in temperature with an effective activation energy of 6.6 eV. Films given a 10 s anneal at <850 °C develop a substantial density of 8 nm grains, making this specific composition an unsuitable candidate for replacing SiO2 as the gate oxide in hyperscaled field-effect transistors.
Supercritical resist drying for isolated nanoline formation
Authors: Namatsu Hideo
Published: July 2002

Supercritical resist drying enables the formation of fine resist patterns with a nanometer-scale resolution. Fine isolated and dense lines of resist collapse when dried by conventional methods after development, thereby lowering the useful resolution of resist patterns. For nanolines, the collapse is due to the swelling of the resist that results from development and rinsing. To prevent collapse, the cause of the swelling must be removed from the resist before drying. The use of supercritical fluid is the most suitable way to do that because such fluid has a diffusion coefficient as large as that of a gas. Supercritical resist drying with carbon dioxide prevents the collapse of isolated lines and enables the formation of nanolines with a width of about 7 nm and a high aspect ratio of over 10 in the case of the negative tone resist of hydrogen silsesquioxane and 100 kV electron beams.
Resist line edge roughness and aerial image contrast
Authors: Shin J. , Han G. , Ma Y. , Moloni K. , Cerrina Franco
Published: July 2002

We report the results of an experimental study of the correlations between line edge roughness (LER) and aerial image contrast for different lithographies in identical processing conditions. The characterization has been performed using atomic force microscopy carbon nanotube tips to image the top and bottom of trenches with very high resolution. Experimental results generally support that higher aerial image contrast leads to lower line edge roughness, but differences exist among the lithographies and resists. Top surface roughness results show similar trends with LER. Higher aerial image modulation also yields higher resist sidewall angle.
Interactions of H2O with SrTiO3(100) surfaces
Authors: Wang Li-Qiong , Ferris K. F. , Herman G. S.
Published: July 2002

Interactions of H2O with SrTiO3(100) surfaces were investigated using temperature-programed desorption (TPD) spectroscopy. TPD spectra show that water desorbs below 300 K on stoichiometric TiO2–terminated SrTiO3(100) surfaces. TPD features at 200–300 K are attributed to the nondissociative adsorption of H2O on cation sites while the TPD feature at 160 K is assigned to the desorption of multilayer water. However, TPD spectra for H2O on reduced SrTiO3(100) surfaces exhibit additional desorption features at 300–500 K, resulting from the dissociative adsorption of water. Comparisons of TPD spectra for H2O on SrTiO3(100) with unreconstructed TiO2(110) and (100) surfaces reveal a structural influence on the water adsorption and desorption behavior.
Study of angular influence of C3H5+ ion deposition on polystyrene surfaces using molecular dynamics simulations
Authors: Jang Inkook , Ni Boris , Sinnott Susan B.
Published: July 2002

The influence of incident angle on the interaction of polyatomic hydrocarbon ions (C3H5+) with polystyrene surfaces is examined using classical molecular dynamics simulations. The forces are determined using the reactive empirical bond order method developed by Tersoff and parametrized by Brenner. The total incident energy is 50 eV and the angles considered are 0° (normal to the surface), 15°, 45°, and 75°. At each angle, the outcomes of 80 trajectories are compiled and averaged. The results show that intact ions scatter from the surface in only 2% of the trajectories and that the ions dissociate in 61% of the trajectories at normal incidence. At 75°, intact ions scatter away in 56% and they dissociate in only 30% of the trajectories. The largest total amount of carbon is deposited at normal incident angles. However, more ions or ion fragments are predicted to remain near the surface (penetrate 3.5–5.5 Å) at 45°. This is because ion fragments tend to penetrate more deeply (6–7 Å) into the surface at smaller angles. Consequently, some inclined angles are found to be most efficient for the deposition of the precursors necessary for polymer thin-film growth.