bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimism vs. Pessimism: Design Decisions in the Face of Process Capability Uncertainty
Authors: Thornton Anna C.
Published: July 2002

Product development firms continually struggle to simultaneously keep product cost low while increasing product quality. This paper focuses on variation and its impact on the quality-failure costs—scrap, rework, extra labor, customer dissatisfaction, and product returns. In many cases, reducing quality failures requires an increase in product cost. Balancing these two costs is challenging because perfect information about process variability is rarely, if ever, available. As a result of process variation uncertainty, there is no clear optimal solution to the quality-failure cost/unit cost tradeoff. The author has observed that companies take one of two approaches to this dilemma: optimistic or pessimistic. The optimistic approach risks high rework costs to ensure the lowest cost product. On the other hand, the pessimistic approach forgoes potential unit cost reductions to avoid any quality failure. This paper presents a utility theory model of decision making under process capability uncertainty. This model is used to describe why either approach can be optimal depending on the organization, market, and product characteristics. In addition, information value theory is applied to explain the relative value of process capability information and variation reduction in the two approaches. The paper uses a frequently encountered design scenario to demonstrate the approach. In addition, a variety of other examples from industry are used to describe how the theory can be applied.
Sizing of Heat Spreaders Above Dielectric Layers
Authors: Chen Calvin , Hodes Marc , Manzione Lou
Published: July 2002

A means to properly size rectangular heat spreaders between a dielectric layer connected to thermal ground and a power device is developed by modeling the problem as a thermal resistance network. Generalized formulas and nondimensional charts to optimize heat spreader thickness and footprint are presented. The power device and heat spreader are assumed to be (concentric) rectangular solids of arbitrary length, width and thickness. The nondimensional results are validated by finite element analysis (FEA) and examples demonstrate the utility of the methodology to thermal design engineers.
Numerical Simulation of Creep-Induced Buckling of Thin-Walled Pipe Liners
Authors: Zhao Qiang , Nassar Raja , Hall David E.
Published: July 2002

Material properties obtained from characterization tests on a representative cured-in-place pipe material have been incorporated into a finite element model which employs a special “composite” beam element. The creep buckling behavior of constrained pipe liners are discussed, and a model correlating the critical time and the applied pressure is proposed. The influence of liner/host pipe geometric parameters on liner buckling is also investigated. The agreement of finite element predictions with physical test data shows the utility of the proposed model.
Compressor Exit Conditions and Their Impact on Flame Tube Injector Flows
Authors: Barker A. G. , Carrotte J. F.
Published: July 2002

Within a gas turbine engine the flow field issuing from the compression system is nonuniform containing, for example, circumferential and radial variations in the flow field due to wakes from the upstream compressor outlet guide vanes (OGVs). In addition, variations can arise due to the presence of radial load bearing struts within the pre-diffuser. This paper is concerned with the characterization of this nonuniform flow field, prior to the combustion system, and the subsequent effect on the flame tube fuel injector flows and hence combustion processes. A mainly experimental investigation has been undertaken using a fully annular test facility which incorporates a single stage axial flow compressor, diffuser, and flame tube. Measurements have been made of the flow field, and its frequency content, within the dump cavity. Furthermore, the stagnation pressure presented to the core, outer and dome swirler passages of a fuel injector has been obtained for different circumferential positions of the upstream OGV/pre-diffuser assembly. These pressure variations, amounting to as much as 20 percent of the pressure drop across the fuel injector, also affect the flow field immediately downstream of the injector. In addition, general variations in pressure around the fuel injector have also been observed due to, for example, the fuel injector position relative to pre-diffuser exit and the flame tube cowl.
In Vivo Calibration of a Femoral Fixation Device Transducer for Measuring Anterior Cruciate Ligament Graft Tension: A Study in an Ovine Model
Authors: Zacharias Isaac , Howell Stephen M. , Hull M. L. , Lawhorn Keith W.
Published: July 2002

Toward developing a transducer for measuring in vivo tension in anterior cruciate ligament grafts in humans, the objectives of this study were to determine the following: (1) whether the calibration of a previously reported femoral fixation device transducer (FDT) (Ventura et al., 1998) is affected by the presence of the graft when implanted in the tibial metaphysis of an ovine model, (2) whether the FDT remains calibrated at 4 weeks postoperatively, and (3) whether the biological incorporation of the graft occurs prior to a change in the FDT calibration. The FDT was implanted in the hind limb of five sheep using an extra-articular procedure. Both the proximal common digital extensor tendon (i.e., graft) and a Teflon-coated wire were looped around the FDT inside a tunnel in the tibial metaphysis. The FDT was calibrated on three occasions using the loop of wire: once intraoperatively before graft insertion, once intraoperatively after graft insertion, and once postoperatively after the animals had been sacrificed at 4 weeks. Following sacrifice, the load transmitted to the FDT by the graft was also determined. The FDT exhibited linear calibration intraoperatively both before and after graft insertion with an average error relative to the calibration before insertion of the graft of −4.6 percent of full-scale load (150 N) and this average relative error was not significantly different from zero p=0.183. After 4 weeks of implantation, the average relative percent error was −5.0 percent and was not significantly different from zero p=0.434 indicating that the FDT remained calibrated in the in vivo environment. Because only 15 percent of the graft tension was transmitted to the FDT after 4 weeks, biological incorporation of the graft preceded the loss of calibration. In light of these findings, the FDT offers the capability of measuring the intra-articular ACL graft tension in vivo in animal models and possibly humans before the biological bond develops and also of monitoring the formation and maturation of the biological bond between a graft and bone tunnel.
Characterization of Delamination in Beams Using Flexural Wave Scattering Analysis
Authors: Ishak S. I. , Liu G. R. , Lim S. P. , Shang H. M.
Published: July 2002

An analytical model for the characterization of delamination in beams using flexural wave scattering analysis is presented. In the beam model of wave propagation, the beam is divided into four regions; to each of them the beam theory of wave propagation is applied to obtain the wave fields excited by a harmonic load on the beam surface. The solution for the entire beam is obtained in terms of the solution for the respective regions using continuity conditions at the junctions. Numerical results on beam displacement for various delamination sizes, materials and excitation frequencies are presented. Experiments using a scanning laser vibrometer on specimens containing simulated delamination are also conducted. The results are then verified by comparing with those obtained by the Strip Element Method (SEM) and experiment. Good agreement is observed between the present model with SEM and experiment.
The Influence of Surface Padding Properties on Head and Neck Injury Risk
Authors: Camacho Daniel L. A. , Nightingale Roger W. , Myers Barry S.
Published: July 2002

A validated computational head–neck model was used to understand the mechanical relationships between surface padding characteristics and injury risk during impacts near the head vertex. The study demonstrated that injury risk can be decreased by maximizing the energy-dissipating ability of the pad, choosing a pad stiffness that maximizes pad deformation without bottoming out, maximizing pad thickness, and minimizing surface friction. That increasing pad thickness protected the head without increasing neck loads suggests that the increased cervical spine injury incidence previously observed in cadaveric impacts to padded surfaces relative to lubricated rigid surfaces was due to increased surface friction rather than pocketing of the head in the pad.
Pressure Measurements and Flow Visualization in a Squeeze Film Damper Operating With a Bubbly Mixture
Authors: San Andre´s Luis , Diaz Sergio E.
Published: July 2002

Squeeze film dampers (SFDs) reduce rotor vibrations and control dynamic instabilities in turbomachinery. Depending on damper geometry and operating conditions, the kinematics of journal motion can induce air ingestion and entrapment, produce lubricant vapor cavitation, or both. Air ingestion is the most common condition found in open ended dampers due to the low levels of external pressurization used in practice. The degrading effect of air entrapment on damper performance not only defies predictive models but also constrains the design of SFDs to a costly trial and error process based on prior experience. The present measurements correlate for the first time dynamic squeeze film pressures and pictures of the flow field with the air volume content in the lubricant mixture of a damper performing circular centered motion. The photographs of the flow field at key instances of journal motion show the development of a non-homogeneous flow with large striated cavities of air that persist even in the regions of positive (above ambient) dynamic pressures.
Finite Element Predictions of the Effect of Diffusion-Accommodated Interfacial Sliding on Thermal Stresses in Cu/Polymer Dielectric and Cu/Oxide Dielectric Single Level Damascene Interconnect Structures
Authors: Kamsah Nazri , Gross Todd S. , Tsukrov Igor I.
Published: July 2002

The finite element method was used to estimate the stresses in single level, 1 μm thick Cu-dielectric interconnect line arrays with Ta liners resulting from heating from 20°C to 400°C assuming that the structure was stress free at 20°C. Benzocyclobutene (BCB) and SiO2 were chosen to represent typical polymer and ceramic dielectric materials being evaluated for Cu damascene interconnect structures. Experimentally observed Cu-Ta and Cu-Cu interfacial sliding was incorporated into the model using a 1 nm thick creep element that was calibrated to match the predictions of a classical diffusion-accommodated sliding model. The effect of Cu-Ta and Cu-Cu interfacial sliding was evaluated by comparing the relaxed and unrelaxed stresses. The effect of line width-to-thickness (w/t) ratio and Ta liner thickness on the shear, normal, and Ta liner-plane stresses at the Cu-Ta-dielectric interface was investigated because this interface is a likely failure site.
Automatic System for Wind Turbine Testing
Authors: Camporeale S. M. , Fortunato B. , Marilli G.
Published: July 2002

An innovative electronic system for testing the performance of wind turbines is presented. The main goal of the system is to increase the accuracy in the measurements of torque and speed for each steady-state point of the turbine characteristic power curve. Another useful advantage provided by the electronic control is given by the possibility of fine tuning the load in order to obtain a large number of steady state experimental points describing the characteristic curve of the turbine. Moreover, the system is suitable for integration into an automatic data acquisition and control system. In the paper the main characteristics of the electronic system are described and compared with a traditional system. This electronic control system is used for testing a small Vertical Axis Wind Turbine in a wind tunnel. The wind turbine is directly coupled to a direct current electric generator, and a chopper, electronically controlled by means of a Pulse Width Modulator, is used to supply the circuit. The electric generator is used for braking the wind turbine at various speeds during the performance test. The experimental results obtained through the proposed system are presented and discussed.
Scale and Lag Effects on Control of Aerodynamic Power and Loads on a HAWT Rotor
Authors: Moriarty P. J. , Eggers, A. J. , Chaney K. , Holley W. E.
Published: July 2002

The effects of rotor scale and control system lag were examined for a variable-speed wind turbine. The scale study was performed on a teetered rotor with radii ranging between 22.5m and 33.75m. A 50% increase in radius more than doubled the rated power and annual energy capture. Using blade pitch to actively control fluctuating flatwise moments allowed for significant reductions in blade mass for a fixed fatigue life. A blade operated in closed-loop mode with a 33.75m radius weighed less than an open-loop blade with a 22.5m radius while maintaining the same fatigue life of 5×109 rotations. Actuator lag reduced the effectiveness of the control system. However, 50% reductions in blade mass were possible even when implementing a relatively slow actuator with a 1 sec. time constant. Other practical limits on blade mass may include fatigue from start/stop cycles, non-uniform turbulence, tower wake effects, and wind shear. The more aggressive control systems were found to have high control accelerations near 60 deg/s2, which may be excessive for realistic actuators. Two time lags were introduced into the control system when mean wind speed was estimated in a rapidly changing wind environment. The first lag was the length of time needed to determine mean wind speed, and therefore the mean control settings. The second was the frequency at which these mean control settings were changed. Preliminary results indicate that quickly changing the mean settings (every 10 seconds) and using a moderate length mean averaging time (60 seconds) resulted in the longest fatigue life. It was discovered that large power fluctuations occurred during open-loop operation which could cause sizeable damage to a realistic turbine generator. These fluctuations are reduced by one half or more when aerodynamic loads are actively controlled.
Suppressing Cracking in Resistance Welding AA5754 by Mechanical Means
Authors: Zhang Hongyan , Senkara Jacek , Wu Xin
Published: July 2002

In this paper mechanical aspects of cracking during single- and multi-spot welding of AA5754 was investigated by both experimental and analytical approaches. The impact of mechanical loading on crack initiation and propagation was studied with the consideration of various process parameters including the loading imposed by electrodes, the formation of liquid nugget, and constraining factors during and after welding. Tensile properties of AA5754 and their dependence on the temperature were tested at room and up to solidus temperatures, in order to provide a reference of cracking stress. Thermal-mechanical analysis was conducted based on the temperature field around the nugget and the state of stress encountered during welding. This analysis revealed that tensile stress might build up in the vicinity of the nugget during cooling, as explained in the experimental observation. General guidelines for suppressing cracking were proposed, i.e., to provide sufficient constraint around the weld spot during and after welding.
A New Fundamental Bioheat Equation for Muscle Tissue—Part II: Temperature of SAV Vessels
Authors: Zhu Liang , Xu Lisa X. , He Qinghong , Weinbaum Sheldon
Published: July 2002

In this study, a new theoretical framework was developed to investigate temperature variations along countercurrent SAV blood vessels from 300 to 1000 μm diameter in skeletal muscle. Vessels of this size lie outside the range of validity of the Weinbaum-Jiji bioheat equation and, heretofore, have been treated using discrete numerical methods. A new tissue cylinder surrounding these vessel pairs is defined based on vascular anatomy, Murray’s law, and the assumption of uniform perfusion. The thermal interaction between the blood vessel pair and surrounding tissue is investigated for two vascular branching patterns, pure branching and pure perfusion. It is shown that temperature variations along these large vessel pairs strongly depend on the branching pattern and the local blood perfusion rate. The arterial supply temperature in different vessel generations was evaluated to estimate the arterial inlet temperature in the modified perfusion source term for the s vessels in Part I of this study. In addition, results from the current research enable one to explore the relative contribution of the SAV vessels and the s vessels to the overall thermal equilibration between blood and tissue.
Microscopic Velocimetry With a Scaled-Up Model for Evaluating a Flow Field Over Cultured Endothelial Cells
Authors: Fukushima Shuichiro , Deguchi Takaaki , Kaibara Makoto , Oka Kotaro , Tanishita Kazuo
Published: July 2002

A microscopic velocimetry technique for evaluating the flow field over cultured endothelial cells was developed. Flow around a cell model scaled up by a factor of 100 was visualized by using an optical microscope and was quantified by using particle-tracking velocimetry. Wall shear stress on the model surface was determined from a two-dimensional velocity field interpolated from measured velocity vectors. Accuracy of the velocimetry was verified by measuring the flow over a sinusoidal cell model that had a wall shear stress profile analytically determined with linear perturbation theory. Comparison of the experimental results with the analytical solution revealed that the total error of the measured wall shear stress was 6 percent.
Direct Simulation Monte Carlo Analysis of Rarefied Gas Flow Structures and Ventilation of Etching Gas in Magneto-Microwave Plasma Etching Reactors
Authors: Ikegawa Masato , Ogawa Yoshihumi , Fukuyama Ryoji , Usui Tatehito , Tanaka Jun’ichi
Published: July 2002

Gas flows in plasma etching reactors for semiconductor fabrication became a chief consideration in designing second-generation reactors with higher etching rates. An axisymmetrical model based on the direct simulation Monte Carlo method has been developed for analyzing rarefied gas flows in a vacuum chamber with the conditions of downstream pressure and gas flow rate. By using this simulator, rarefied gas flows with radicals and etch-products were calculated for microwave-plasma etching reactors. The results showed that the flow patterns in the plasma chamber strongly depend on the Knudsen number and the gas-supply structure. The ventilation of the etch-products in the plasma chamber was found to be improved both for higher Knudsen numbers and for gas-supply structures of the downward-flow type, as compared with those of the radial-flow or upward-flow types.
The Effect of Uniform Blowing on the Flow Past a Circular Cylinder
Authors: Mathelin Lionel , Bataille Franc¸oise , Lallemand Andre´
Published: July 2002

This work describes blowing through the whole surface of a porous circular cylinder for the control of the near wake dynamics and the thermal protection of the surface. The flow past the cylinder is numerically studied and the blowing is modeled. Comparisons with experimental data are used for validation. It is shown that the blowing tends to increase the boundary layer thickness, to promote its separation and to decrease the viscous drag induced. Similarly, the convective heat transfer is lowered, and in the case of a nonisothermal blowing, the surface is very effectively protected from the hot free stream flow. The near wake is also affected. The vortex shedding frequency is shown to decrease when blowing occurs and a qualitative model is presented to identify the different mechanisms.
Machining as a Wedge Indentation
Authors: Madhavan V. , Chandrasekar S. , Farris T. N.
Published: July 2002

A case is made for the consideration of single-point machining of ductile metals as a special type of wedge indentation process. A general-purpose finite element analysis of machining using iterative rezoning is developed based on this analogy. The accuracy of this analysis, which does not incorporate any separation criterion, is limited only by our knowledge of the material properties and the friction conditions at the tool-chip interface. Strain hardening, strain rate effects, and the temperature dependence of the properties of the work material can be taken into consideration. While Coulomb friction is assumed at the chip-tool interface in the present model, it can easily be reformulated to include more complicated frictional interactions such as adhesion. An analysis of the cutting/indentation of an isotropic work-hardening material at slow speeds under two different friction conditions is presented. It is shown that many of the important features of machining processes are consistently reproduced by the analysis. [S0021-8936(00)03501-7]
Second-Moment Closure Model for IC Engine Flow Simulation Using Kiva Code1
Authors: Yang S. L. , Peschke B. D. , Hanjalic K.
Published: July 2002

The flow and turbulence in an IC engine cylinder were studied using the SSG variant of the Reynolds stress turbulence closure model. In-cylinder turbulence is characterized by strong turbulence anisotropy and flow rotation, which aid in air-fuel mixing. It is argued that solving the differential transport equations for each turbulent stress tensor component, as implied by second-moment closures, can better reproduce stress anisotropy and effects of rotation, than with eddy-viscosity models. Therefore, a Reynolds stress model that can meet the demands of in-cylinder flows was incorporated into an engine flow solver. The solver and SSG turbulence model were first successfully tested with two different validation cases. Finally, simulations were applied to IC-engine like geometries. The results showed that the Reynolds stress model predicted additional flow structures and yielded less diffusive profiles than those predicted by an eddy-viscosity model. [S0742-4795(00)00101-0]
Modal Effects on the Local Heat Transfer Characteristics of a Vibrating Body
Authors: Murphy K. D. , Lambert, T. A.
Published: July 2002

This is an experimental investigation of the effects of forced transverse vibrations on the local heat transfer characteristics of a heated, pinned-pinned beam. In particular, the response of a cylindrical beam near its first two natural frequencies, corresponding to the first two vibration modes, is considered. The results show that there is a strong spatial variation in the local Nusselt number and that these variations are closely related to the mode shape of the response. Because the heat transfer measurements were taken at the resonance frequencies, where the structural response was greatest, the measured Nusselt numbers provide an upper bound for the increased convection due to flexible body vibrations, i.e., in the absence of any rigid-body mode. The possibility of large-amplitude nonlinear vibrations are discussed (though they were not witnessed experimentally) in a theoretical framework. [S0022-1481(00)01702-3]
Magnetic Erasures Due to Impact Induced Interfacial Heating and Magnetostriction
Authors: Suk M. , Dennig P. , Gillis D.
Published: July 2002

High-velocity intermittent contacts between a slider and a disk may lead to data erasure due to interfacial heating and high-speed mechanical contact stresses. These potential modes of erasure are investigated by artificially introducing high contact stresses that are not likely to be observed in disk drives. Nevertheless, the mechanisms of erasure are delineated in this study with little ambiguity by comparing the results from three different substrate materials, namely Al-Mg, glass, and Si. We show that written flux patterns can be erased if either the substrate material has low thermal conductivity or if the magnetic layer is damaged. We conclude that if the disk is not plastically damaged by high-speed contacts, then the magnetostriction effect or stress-induced erasure is insignificant. In this case, the dominant factor in erasure is a rise in the interfacial temperature, which is exacerbated by low thermal conductivity of the substrate. [S0742-4787(00)03401-9]
Nonaxisymmetric Turbine End Wall Design: Part II—Experimental Validation
Authors: Hartland J. C. , Gregory-Smith D. G. , Harvey N. W. , Rose M. G.
Published: July 2002

The Durham Linear Cascade has been redesigned with the nonaxisymmetric profiled end wall described in the first part of this paper, with the aim of reducing the effects of secondary flow. The design intent was to reduce the passage vortex strength and to produce a more uniform exit flow angle profile in the radial direction with less overturning at the wall. The new end wall has been tested in the linear cascade and a comprehensive set of measurements taken. These include traverses of the flow field at a number of axial planes and surface static pressure distributions on the end wall. Detailed comparisons have been made with the CFD design predictions, and also for the results with a planar end wall. In this way an improved understanding of the effects of end wall profiling has been obtained. The experimental results generally agree with the design predictions, showing a reduction in the strength of the secondary flow at the exit and a more uniform flow angle profile. In a turbine stage these effects would be expected to improve the performance of any downstream blade row. There is also a reduction in the overall loss, which was not given by the CFD design predictions. Areas where there are discrepancies between the CFD calculations and measurement are likely to be due to the turbulence model used. Conclusions for how the three-dimensional linear design system should be used to define end wall geometries for improved turbine performance are presented. [S0889-504X(00)01002-3]
A Relationship Between Defective Systems and Unit-Rank Modification of Classical Damping
Authors: Prells Uwe , Friswell Michael I.
Published: July 2002

A common assumption within the mathematical modeling of vibrating elastomechanical system is that the damping matrix can be diagonalized by the modal matrix of the undamped model. These damping models are sometimes called “classical” or “proportional.” Moreover it is well known that in case of a repeated eigenvalue of multiplicity m, there may not exist a full sub-basis of m linearly independent eigenvectors. These systems are generally termed “defective.” This technical brief addresses a relation between a unit-rank modification of a classical damping matrix and defective systems. It is demonstrated that if a rank-one modification of the damping matrix leads to a repeated eigenvalue, which is not an eigenvalue of the unmodified system, then the modified system is defective. Therefore defective systems are much more common in mechanical systems with general viscous damping than previously thought, and this conclusion should provide strong motivation for more detailed study of defective systems. [S0739-3717(00)00602-4]
A Study of Solid CO2/H2O and CO2/CH3OH by XPS
Authors: Dillingham T. R. , Cornelison D. M.
Published: July 2002

High quality solid CO2/H2O and CO2/CH3OH films have been grown on a stainless steel cold-finger using a continuous flow liquid nitrogen system. The solid (or ice) was formed from research grade (99.995% min. purity) isotopic 13CO2 gas, and ultrapure water vapor or methanol vapor. The isotopic 13CO2 gas was used to distinguish it from any background CO2 gas in the vacuum system. The gases were mixed in a stainless steel prechamber with the pressure monitored using an MKS capacitance manometer. The base pressure in the analysis chamber was less than 5 × 10−10 T prior to deposition and upon gas introduction was inceased, using a precision leak valve, to approximately 2 × 10−8 T. Films were grown at this pressure for approximately 1 h. Gas purity was monitored using a Balzers Prisma QMS 300 quadrupole mass spectrometer. The nucleated films were characterized using x-ray photoelectron spectroscopy (XPS). The reported spectra include survey and high resolution scans of the major photoelectron peaks.
Effect of a thin Ni layer on hydrogenation and thermal release characteristics of Ti thin films
Authors: Shi L. Q. , Zhou Z. Y. , Zhao G. Q.
Published: July 2002

Carbon and oxygen contamination on the Ti surface strongly influences hydrogen absorption and desorption, and it can even passivate the surface completely. The effect of C and O on the hydrogen absorption and thermal release on Ti films was investigated by using high-energy non-Rutherford backscattering and elastic recoil detection techniques. The experimental results show that the concentration gradient in the region of about 300 nm near the surface is very large due to the joint contamination of about 1.26×1016 atoms/cm2 of C and 2.5×1016 atoms/cm2 of O; also, the thermal releasing temperature increased greatly. A thin Ni film coated on the Ti film may considerably reduce the contamination of gaseous impurities, in particular C, and prevents further oxidation and improve the absorption and desorption of hydrogen.
The effect of photoacid generator structure on deep ultraviolet resist performance
Authors: Ablaza Sheri L. , Cameron James F. , Xu Guangyu , Yueh Wang
Published: July 2002

The structural influence of photoacid generators on deep ultraviolet resist performance is investigated in both high and low activation energy resist systems. The lithographic behavior of the photoacid generator is considered in terms of the structure of the photogenerated acid and the light sensitive chromophore. First, the lithographic impact of the photogenerated acid is investigated in terms of acid strength and acid size in resists optimized for high and low temperature processing, respectively. Dissolution kinetics, contrast curve data, and absorbance data are presented for a series of high and low activation energy resists in which the structure of the photogenerated acid is systematically varied. The results of these studies are discussed in terms of the photogenerated acid, emphasizing the impact of acid strength and size on lithographic performance and resist dissolution rate kinetics for each resist platform. Second, the structural influence of the light sensitive photoacid generator (PAG) chromophore is investigated by comparing the lithographic performance and acid generating efficiency of iodonium and sulfonium salt PAGs. Last, correlations of lithographic performance and dissolution rate kinetics are probed in terms of resist type (high and low temperature systems) and PAG structure.
Composition Gradients in Ni–Fe Alloy Films Produced by Vapor Deposition from a Tungsten Boat
Authors: Carson K. R. , Rudee M. L.
Published: July 2002

When an alloy film is produced by evaporation from a limited volume of material in a tungsten boat, differences in the vapor pressures of the constituents can produce different compositions through the thickness of the film. These composition changes can affect magnetic properties; e.g., it has been suggested that magnetization gradients produce anomalies in spin wave spectra. We have measured the variation of composition through the thickness of Ni–Fe films by moving a long substrate past a collimated source during deposition from a boat. It is observed that for a wide range of deposition temperatures and integrated thickness the results nearly coincide if all of the data are plotted as a function of normalized fractional thickness. For starting material of 80.89% Ni, evaporated to completion, the initial composition is 74% Ni and rises linearly to 81% Ni at 0.8 fractional thickness. A steeply rising exponential region follows. The origin of these regions will be discussed.
Fundamental Electronic Transport Properties of GaAs Evaporated Films
Authors: Takahashi Kiyoshi
Published: July 2002

The fundamental electronic transport properties of GaAs evaporated films have been studied by means of resistivity vs temperature measurements, transient responses of photoconduction, and space charge limited current characteristics. The films were n type, with carrier concentrations of ∼1.4×1010/cm3 and electron mobilities of 4.4×102 cm2/V⋅sec at room temperature. Trap densities were ∼1014/cm3 and trap levels were found to be approximately 0.45 eV below the conduction band edge.
Reactive Scattering of N2O Molecular Beams from Clean and Carbon-Covered (100) Platinum Single-Crystal Surfaces
Authors: West L. A. , Somorjai G. A.
Published: July 2002

Thermal energy molecular beams of N2O have been scattered from a platinum (100) surface maintained in the temperature range 900–1500 K in an ultrahigh vacuum chamber. The angular distribution of the scattered beams was monitored with a quadrupole mass spectrometer, the target surface structure by low energy electron diffraction, and the composition by Auger spectroscopy. The effect of surface temperature and surface structure on the surface decomposition of N2O has been studied. At 1200 K, using a clean surface, the angular distribution of one of the reaction products, NO, follows the cosine law, but deviations from this behavior seem to occur if the surface is covered by a layer of carbon. At still higher temperatures N2O reacts with the carbon layer on the surface and removes it by the oxidation reaction N2O+C→CO+N2. The mechanisms of reactive scattering based on the experimental observations are discussed.
A Quantitative Study of Nucleation and Growth of Copper I—Oxide on Copper Single Crystals
Authors: Jardinier-Offergeld M. , Bouillon F.
Published: July 2002

A microgravimetric study shows that the rate of oxidation of the (100) face of copper is convenient for the observation of the different steps of the process: induction, nucleation, and growth of the oxide particles. The rate of those steps and the number of nuclei depend upon crystallographic orientation of the metal, temperature of reaction, and pressure of oxygen. Sticking probabilities and activation energies of the different steps have been determined. Our results show under which conditions Rhead's theoretical scheme founded on surface diffusion remains valid.
Retarding-Field—Cylindrical-Mirror Analyzer
Authors: Gerlach Robert L.
Published: July 2002

An electron energy analyzer system incorporating a two-stage, spherical retarding-field–cylindrical-mirror analyzer as well as high current, coaxial, and glancing incidence electron guns is described. The retarding field and cylindrical mirror analyzers act as high-pass and band-pass energy filters, respectively. The resulting two-stage device has the advantages of both types of analyzers—low shot noise, high transmission, adjustable energy resolution, nearly constant energy resolution and transmission as a function of band-pass energy, and relative insensitivity to sample positioning. The glancing incidence electron gun is mounted directly on the front of the analyzer and is bore sighted onto the sample, thereby avoiding the need for deflection electrodes. Design and performance of this system are investigated.
Sticking Coefficient of CO2 on Solid H2O Films
Authors: Cazcarra V. , Bryson C. E. , Levenson L. L.
Published: July 2002

A molecular beam method has been used to measure the sticking coefficient γ of CO2 molecules on thin films of solid H2O. Impingement rates were below 1014 molecules cm−2 sec−1, and the CO2 gas temperature was 184 K. The substrate temperature TS was varied from 65.5–76.4 K. At TS=76.4 K, γ was initially near unity, but decreased with increasing CO2 coverage until γ≃0 at approximately monolayer coverage. When TS was below 76.4 K, the initial γ was also close to unity. As the CO2 coverage increased, γ decreased to a minimum value at about one monolayer coverage. However, γ again increased with time as CO2 continued to be deposited. These results are discussed in terms of a simple nucleation theory.
Some Experimental Effects in Films of Ordered Matter
Authors: Guyon E.
Published: July 2002

The existence of boundary layers, having properties different from the bulk, influences considerably the ordering properties of thin films of condensed matter. First, we will review the problem of size effects in superconducting as well as in superfluid helium films. Liquid crystals films offer another class of ordered systems in which similar concepts can be applied. The physicochemical understanding of the boundary effects (role of the elastic distortion and of the interfacial chemical energy) and the bulk ordering mechanisms will be discussed and the analogies with the previous low temperature examples studied in the framework of the Landau model of phase transitions. A direct approach of the dynamic behavior is also possible due to macroscopic relaxation times.
Computer Controlled Pattern Generating System for use with Electron-Beam Writing Instruments
Authors: Spicer D. F. , Rodger A. C. , Varnell G. L.
Published: July 2002

Recent advances in electron sources and electron resists have resulted in a significant increase in potential exposure rate in electron-beam writing instruments. This in turn places stringent requirements on the pattern generating electronics which must be fast enough to avoid their limiting potential system throughout, yet flexible enough to be capable of creating all normally required geometries. A computer-controlled pattern generation system is described which is designed to meet these requirements. In this system, the speed limitation due to the calculation and data-transfer rate of modern minicomputers is avoided by the use of an auxiliary special-purpose logic processor. Patterns are built up from a basic trapezoid shape with two sides parallel to rectangular cartesian coordinate axes. The computer has only to specify the basic parameters defining a trapezoid and the auxiliary processor will then output coordinates representing the end points of lines defining the figure in a raster-scan format. These coordinates, which may be generated at rates up to 1 MHz are passed to a pair of precision ramp generators. The ramp generators, which are based on commercially available 16-bit digital-to-analog converters, then produce the analog deflection signals needed to define the line, at a sweep rate which may be varied under computer control over six orders-of-magnitude. Particular care has been taken to reduce the switching spikes, inherent in digital-to-analog converters, to negligible proportions on the output waveform.
157 nm resist materials: Progress report
Authors: Brodsky Colin , Byers Jeff , Conley Will , Hung Raymond , Yamada Shintaro , Patterson Kyle , Somervell Mark , Trinque Brian , Tran H. V. , Cho Sungseo , Chiba Takashi , Lin Shang-Ho , Jamieson Andrew , Johnson Heather , Vander Heyden Tony , Willson C. Grant
Published: July 2002

Many semiconductor device manufacturers plan to make products with 157 nm lithography beginning in 2004. There is, at this time, no functional photoresist suitable for 157 nm exposure. Developing resist materials for 157 nm lithography is particularly challenging since water, oxygen, and even polyethylene are strongly absorbing at this wavelength. A modular approach to the design of a single layer resist for 157 nm has been undertaken. In this approach, the resist has been conceptually segmented into four functional modules: an acidic group, an acid labile protecting group, an etch resistant moiety, and a polymer backbone. Each of these modules has an assigned function and each must be transparent at 157 nm. Progress has been made toward finding candidate structures for each of these modules. We have demonstrated that acidic bistrifluoromethylcarbinols are very transparent at 157 nm and function efficiently in chemically amplified resists with both high and low activation energy protecting groups. Judicious incorporation of fluorine in acrylates and alicyclics has provided etch resistant polymers with greatly improved transparency at 157 nm. In particular, esters of poly(α-trifluromethylacrylic acid) are far more transparent than their protio analogs. The Diels–Alder adducts derived from reaction of these and other fluorinated alkenes with cyclopentadiene offer a route to a wide range of alicyclic monomers that show great promise as transparent, etch resistant platforms for the design of 157 nm resists. Polymers of this sort with absorbance below 2 per micrometer are reported.
Electron-beam direct writing using RD2000N for fabrication of nanodevices
Authors: Dutta A. , Lee S. P. , Hayafune Y. , Oda S.
Published: July 2002

A simple but potent method for electron-beam (EB) direct writing is introduced. This method is based on the use of negative electron-beam resist RD2000N. The resist offers high sensitivity to EB exposure and high resistance to halide plasma etching conditions, which is ideal for application in Si/SiO2 based nanodevice fabrication. Dot exposure shows that dots of a minimum diameter of 16 nm could be patterned using this resist. Linear arrays of dots, connected to each other by very narrow constrictions, are patterned using this resist. When transferred to a thin silicon-on-insulator layer, by reactive ion etching, this structure forms a multiple tunnel junction. Memory devices based on this multiple tunnel junction are fabricated. Memory operation is observed at 20 K.
Microcrystalline silicon by plasma enhanced chemical vapor deposition from silicon tetrafluoride
Authors: Cicala G. , Capezzuto P. , Bruno G.
Published: July 2002

The amorphous and microcrystalline silicon growth from SiF4–H2–He plasmas has been studied by exploring various parameters, such as He addition, rf power, H2 dilution, and frequency. The dilution of SiF4–H2 plasmas with He gas has been found to promote the crystalline phase and entirely microcrystalline silicon films have been obtained at low temperature (120 °C) under optimized experimental conditions. All the obtained results are discussed on the basis of etching/growth competition mechanism, in which the etching process by F atoms is selective for the amorphous phase. As such, all the experimental conditions enhancing the etching channel let the microcrystalline growth prevail. The net deposition rate, monitored by the laser reflectance interferometry, results from the difference between growth rate, rG, and etching rate, rE. Optical emission spectroscopy is a powerful in situ diagnostic tool to monitor the crystallinity degree in the material, since the [F*]⋅[He*]/[SiF2*]⋅[Hα] ratio, obtained from the peak intensities and called the Γ ratio, has been found to be proportional to the rE/rG ratio.
Theoretical study of the threshold field for field electron emission from amorphous diamond thin films
Authors: Xu N. S. , She J. C. , Huq S. E. , Deng S. Z. , Chen J.
Published: July 2002

Theoretical and numerical treatments were devoted to the derivation of the threshold field for field electron emission from amorphous diamond thin films. Heavily doped n++-Si in the geometry of the tip was used as the cathode substrate. A three-step process involving internal emission, electron transport in the coating, and vacuum emission was employed to understand the emission. The derivation results predict that the potential barrier height at the Si-diamond interface is the main parameter that governs the threshold field for emission, which is consistent with the experimental phenomena that have been observed.
Interface engineering and graded films: Structure and characterization
Authors: Bull S. J.
Published: July 2002

The properties and performance of most bulk materials and coatings are controlled by interfaces. For bulk materials the surface is the most important interface, though grain and phase boundaries may also play a role in dictating performance. For coatings the coating-substrate interface is equally important and other internal interfaces may also contribute to behavior. This article reviews the effect of interfaces on the hardness of bulk materials, single and multilayer coatings highlighting the importance of engineering interfaces with high strength if coatings with optimum properties are to be achieved. A simple model is introduced which enables the effect of such interfaces to be more fully appreciated. The possibility of using graded compositions, such as ion implanted layers, to improve performance is also discussed in light of this model.
Recrystallization effects in Cu electrodeposits used in fine line damascene structures
Authors: Jiang Qing-Tang , Thomas Michael E.
Published: July 2002

Resistance transformations in blanket films and damascene lines of electroplated Cu were investigated to gain insight regarding the recrystallization kinetics of electrochemically deposited Cu in constrained deep submicron features. The study examined grain transformations in blanket Cu films with thicknesses ranging from 0.8 to 3.3 μm and Cu damascene lines with widths from 0.25 μm to approximately 1.0 μm. Bulk film resistivity changes were found to be directly related to new grain formation and growth (recrystallization) observed in the films. By monitoring the electrical properties of the continuous and patterned films, it was observed that damascene lines of Cu required longer times to achieve the same degree of bulk resistivity change when compared with blanket films. For example, at room temperature, a 0.35 μm wide×0.8 μm high Cu line underwent only half the resistive transformation over an 865 h period (36 days) that was completed in 120 h (5 days) in a 0.8 μm blanket Cu film. Microstructural images of damascene structures, using a focused ion-beam microscope, clearly indicated that wider Cu lines transform much faster than narrower ones. To investigate the recrystallization kinetics, samples, prepared under identical conditions, were annealed at different temperatures and times. The recrystallization activation energies derived using an Arrhenius model (under isoresistivity conditions) were found to be approximately 0.8 eV for all Cu films and lines regardless of geometry. The study indicates that although the overall rate of recrystallization of Cu was very different and dependant on physical geometrical constraints, the grain growth mechanism was the same for all Cu films and lines.
Calibrated magnetic force microscopy measurement of current-carrying lines
Authors: Yongsunthon R. , McCoy J. , Williams E. D.
Published: July 2002

An experimental configuration for evaluating the magnetic force microscopy (MFM) instrument response for known structures, such as that around current-carrying lines containing defects of simple geometry, has been developed. The configuration includes mechanisms for nulling electrostatic potential differences between the sample and probe, and for providing an in situ reference structure adjacent to the test structure. The reference structure is used to normalize the signal magnitude from the test structure. The instrumental response function was determined iteratively by comparing the forward convolution of the calculated magnetic response with the measured signal from a 10 μm wide, 110-nm-thick Cr/Au-on-SiO2 structure. This response function was then used in a maximum entropy method deconvolution of signals from a 10 μm wide line containing a 3 μm×40 μm slot. Preliminary results show that meaningful relative quantification of the MFM signal amplitude can be achieved to within 10% and absolute current variations can be detected to at least 10%.