bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Management Strategies for Embedded Electronic Components of Wearable Computers
Authors: Egan Eric , Amon Cristina H.
Published: July 2002

Wearable computers are rugged, portable computers that can be comfortably worn on the body and easily operated for maintenance applications. The recently developed process of Shape Deposition Manufacturing has created the opportunity to embed the electronics of wearable computers in a polymer composite substrate. As both a protective outer case and a conductive heat dissipating medium, the substrate satisfies two basic constraints of wearable computer design: ruggedness and cooling efficiency. One such application of embedded electronics is the VuMan3R, a wearable computer designed and manufactured at Carnegie Mellon University for aircraft maintenance. This paper combines finite element numerical simulations, physical experimentation, and analytical models to understand the thermal phenomena of embedded electronic design and to explore the thermal design space. Numerical models ascertain the effect of heat spreaders and polymer composite substrates on the thermal performance, while physical experimentation of an embedded electronic artifact ensures the accuracy of the numerical simulations and the practicality of the thermal design. Analytical models using thermal resistance networks predict the heat flow paths within the embedded electronic artifact as well as the role of conductive fillers used in polymer composites. [S1043-7398(00)00102-X]
A Numerical Study of the Thermal Performance of a Tape Ball Grid Array (TBGA) Package
Authors: Sathe Sanjeev B. , Sammakia Bahgat G.
Published: July 2002

This paper deals with the thermal management of a TBGA chip carrier package. In TBGA packages the backside of the chip is available for heat sink or heat spreader (cover plate) attach. By attaching a heat sink directly to the chip and using a thin layer of high thermal conductivity adhesive, a very low internal thermal resistance can be achieved. The package is attached to an organic card and placed vertically in a channel. A three-dimensional conjugate heat transfer model is used, accounting for conduction and radiation in the package and card and convection in the surrounding air. A simplified turbulence model is developed to predict temperatures in the low Re turbulence regime. A parametric study is performed to evaluate the effects of card design, air velocities, interconnect thermal conductivities and thermal radiation on the chip junction temperatures. An experimental study was also conducted to verify the model. Even though the geometry is highly complex due to the multilayer construction of the module and the card, agreement between the model and the experimental measurement is excellent. It was shown that radiation heat transfer can be an equally significant mode as convection in the natural convection regime. [S1043-7398(00)01302-5]
Computational Modeling and Validation of the Encapsulation of Plastic Packages by Transfer Molding
Authors: Nguyen L. , Quentin C. , Lee W. , Bayyuk S. , Bidstrup-Allen S. A. , Wang S.-T.
Published: July 2002

This paper presents, discusses, and compares results from experimental and computational studies of the plastic encapsulation process for a 144-lead TQFP package. The experimental results were obtained using an instrumented molding press, while the computational predictions were obtained using a newly-developed software for modeling transfer molding processes. Validation of the software is emphasized, and this was done mainly by comparing the computational results with the corresponding experimental measurements for pressure, temperature, and flow front advancement in the cavities and runners. The experimental and computational results were found to be in good agreement, especially for the flow-front shapes and locations. [S1043-7398(00)00502-8]
On the Performance of Hybrid Foil-Magnetic Bearings
Authors: Heshmat H. , Chen H. Ming , Walton, J. F.
Published: July 2002

Recent technological advancements make hybridization of the magnetic and foil bearings both possible and extremely attractive. Operation of the foil/magnetic bearing takes advantage of the strengths of each individual bearing while minimizing each other’s weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speeds. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both. To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed. [S0742-4795(00)01201-1]
The IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
Authors: Wagner W. , Cooper J. R. , Dittmann A. , Kijima J. , Kretzschmar H.-J. , Kruse A. , Maresˇ R. , Oguchi K. , Sato H. , Sto¨cker I. , Sˇifner O. , Takaishi Y. , Tanishita I. , Tru¨benbach J. , Willkommen Th.
Published: July 2002

In 1997, the International Association for the Properties of Water and Steam (IAPWS) adopted a new formulation for the thermodynamic properties of water and steam for industrial use. This new formulation, called IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS-IF97), replaces the previous industrial formulation, IFC-67, that had formed the basis for power-plant calculations and other applications in energy engineering since the late 1960’s. IAPWS-IF97 improves significantly both the accuracy and the speed of the calculation of the thermodynamic properties compared with IFC-67. The differences between IAPWS-IF97 and IFC-67 will require many users, particularly boiler and turbine manufacturers, to modify design and application codes. This paper summarizes the need and the requirements for such a new industrial formulation and gives the entire numerical information about the individual equations of IAPWS-IF97. Moreover, the scientific basis for the development of the equations is summarized and the achieved quality of IAPWS-IF97 is presented regarding the three criterions accuracy, consistency along region boundaries, and computation speed. For comparison, corresponding results for the previous standard IFC-67 are also presented. [S0742-4795(00)02201-8]
Flutter Limits and Behaviors of a Flexible Thin Sheet in High-Speed Flow— I: Analytical Method for Prediction of the Sheet Behavior
Authors: Yamaguchi Nobuyuki , Yokota Kazuhiko , Tsujimoto Yoshinobu
Published: July 2002

An analytical method is proposed for the prediction of fluttering of a flexible thin sheet or web swept by fluid flow. It assumes self-excited aeroelastic oscillation of the sheet with infinitesimally small amplitude. The flow and the sheet motion are expressed by distributed vortices over the sheet and the wake, and by bending motions of a number of short segments constituting the sheet. The obtained system of equations determines the flutter limits, the oscillation modes and frequencies. The method treats particularly well the situation of very low mass ratios where the modes are far from those in vacuum and progressive waves are predominant. [S0098-2202(00)01101-9]
High Pressure Annular Two-Phase Flow in a Narrow Duct: Part I—Local Measurements in the Droplet Field
Authors: Trabold Thomas A. , Kumar Ranganathan
Published: July 2002

Detailed measurements have been made in a high pressure, adiabatic (boiled at the inlet) annular flow in a narrow, high aspect ratio duct using a gamma densitometer, hot-film anemometer and high-speed video photography. Measurements of void fraction, droplet frequency, velocity, drop size, and interfacial area concentration have been made to support the three-field computational capability. An important aspect of this testing is the use of a modeling fluid (R-134a) in a vertical duct which permits visual access in annular flow. This modeling fluid accurately simulates the low liquid-to-vapor density ratio of steam-water flows at high pressures. These measurements have been taken in a narrow duct of hydraulic diameter 4.85 mm, and a cross-section aspect ratio of 22.5. However, the flow displays profiles of various shapes not only in the narrow dimension, but also in the width dimension. In particular, the shape of the void profiles depends on the entrained droplet flux from the edges in the vapor core. The average diameter from these profiles compare well with the models developed in the literature. Interfacial area concentration for these low density ratio flows is higher than the highest concentration reported for air-water flows. Video records show that along with the bow-shaped waves, three-dimensional λ-shaped waves appear in annular flows for high flow rates. [S0098-2202(00)00902-0]
Kinematic Analysis and Optimization of a New Three Degree-of-Freedom Spatial Parallel Manipulator
Authors: Carretero J. A. , Podhorodeski R. P. , Nahon M. A. , Gosselin C. M.
Published: July 2002

A study of the kinematic characteristics of a three degree-of-freedom (dof) parallel mechanism is presented. The architecture of the mechanism is comprised of a mobile platform attached to a base through three identical prismatic-revolute-spherical jointed serial linkages. The prismatic joints are considered to be actuated. These prismatic actuators lie on a common plane and have radial directions of action. The mechanism’s inverse displacement solution is obtained. Since the mechanism has only 3 dof, constraint equations describing the inter-relationship between the six motion coordinates are derived. These constraints allow the definition of parasitic motions, i.e., motions in the three unspecified motion coordinates. Architecture optimization of the device is undertaken demonstrating that specific values of design variables allow minimization of parasitic motion. [S1050-0472(00)00101-X]
A New Neighborhood Function for Discrete Manufacturing Process Design Optimization Using Generalized Hill Climbing Algorithms
Authors: Vaughan Diane E. , Jacobson Sheldon H. , Armstrong Derek E.
Published: July 2002

Discrete manufacturing process design optimization can be difficult, due to the large number of manufacturing process design sequences and associated input parameter setting combinations that exist. Generalized hill climbing algorithms have been introduced to address such manufacturing design problems. Initial results with generalized hill climbing algorithms required the manufacturing process design sequence to be fixed, with the generalized hill climbing algorithm used to identify optimal input parameter settings. This paper introduces a new neighborhood function that allows generalized hill climbing algorithms to be used to also identify the optimal discrete manufacturing process design sequence among a set of valid design sequences. The neighborhood function uses a switch function for all the input parameters, hence allows the generalized hill climbing algorithm to simultaneously optimize over both the design sequences and the inputs parameters. Computational results are reported with an integrated blade rotor discrete manufacturing process design problem under study at the Materials Process Design Branch of the Air Force Research Laboratory, Wright Patterson Air Force Base (Dayton, Ohio, USA). [S1050-0472(00)01002-3]
Recent Research and Development Relating to Platform Requalification
Authors: Moan Torgeir
Published: July 2002

Recent efforts on wave loads and their structural effects, ultimate and fatigue resistance, and structural reliability issues relating to requalification of jackets are reviewed. The emphasis is on experiences with North Sea structures. [S0892-7219(00)01201-2]
Autonomous Calibration of Hexapod Machine Tools1
Authors: Zhuang Hanqi , Liu Lixin , Masory Oren
Published: July 2002

Hexapod machines are emerging as a new type of CNC machine tools. Among other things, stringent calibration is an important means to improve their accuracy. Traditionally, to perform system calibration, one needs to measure a number of machine poses using an external measuring device. However, this process is often labor-intensive and invasive, and difficult for on-line calibration. In this paper, a systematic way of self-calibrating a hexapod machine tool is introduced. By adding a small number of redundant internal sensors, errors of the hexapod machine tool can be measured. This approach has the potential of automatically producing high accuracy measurement data over the entire workspace of the system with an extremely fast measurement rate. Once the measurement data is available, a recursive filter is applied to estimate machine parameter errors from the predicted geometric errors, and to update the model residing in the machine controller. Thus, it is possible to dynamically calibrate and compensate for various types of machine errors including those induced by thermal and loading variations, without interrupting the normal operation of the machine tool. To verify the concept, preliminary experimental studies were conducted on a Stewart platform built at Florida Atlantic University. [S1087-1357(00)70901-4]
New Concept of Equivalent Inherent Strain for Measuring Axisymmetric Residual Stresses
Authors: Chen Jun , Terasaki Toshio , Akiyama Tetsuya , Kishitake Katsuhiko
Published: July 2002

A new concept, the equivalent inherent strain gθeq, is proposed for measuring axisymmetric residual stresses, based on the inherent strain theory. gθeq is a parameter obtained by incorporating the radial inherent strain component into the tangential inherent strain component in computing the axially uniform axisymmetric residual stresses. The application of this concept can avoid the restriction of radial inherent strain component estimation and hence leads to a more simple and accurate method for measuring axisymmetric residual stresses. Experimental measurement and numerical simulation were carried out to demonstrate that this method has both the simplicity of the Sachs method and the high accuracy of the inherent strain method. [S1087-1357(00)70402-3]
The Spin-Off of Particles on a Magnetic Disk
Authors: Li Yufeng , Sharma Vinod
Published: July 2002

A spin-off ratio is used in this study to assess the repelling capability of a disk surface to thermal asperity for MR drives. A test methodology is described and a simple model is developed. Three types of spherical particles with different size and material properties are used in this study to evaluate the spin-off ratios of disks from various manufacturers and with different lubricant thickness and texture roughness. It is found that the dominant factors determining whether a particle is spun off a disk surface are the stiction force and the centrifugal force. Particle size and material properties, disk spinning speed, disk radius, surface tension and contact angle have significant effects on the spin-off ratio, while lubricant thickness and disk surface roughness have little effect. The manufacturing process and material used to produce a disk also affect how well the disk behaves when thermal asperity is a concern. [S0742-4787(00)03901-1]
Transonic Aerodynamic Losses Due to Turbine Airfoil, Suction Surface Film Cooling
Authors: Jackson D. J. , Lee K. L. , Ligrani P. M. , Johnson P. D.
Published: July 2002

The effects of suction surface film cooling on aerodynamic losses are investigated using an experimental apparatus designed especially for this purpose. A symmetric airfoil with the same transonic Mach number distribution on both sides is employed. Mach numbers range from 0.4 to 1.24 and match values on the suction surface of airfoils from operating aeroengines. Film cooling holes are located on one side of the airfoil near the passage throat where the free-stream Mach number is nominally 1.07. Round cylindrical and conical diffused film cooling hole configurations are investigated with density ratios from 0.8 to 1.3 over a range of blowing ratios, momentum flux ratios, and Mach number ratios. Also included are discharge coefficients, local and integrated total pressure losses, downstream kinetic energy distributions, Mach number profiles, and a correlation for integral aerodynamic losses as they depend upon film cooling parameters. The contributions of mixing and shock waves to total pressure losses are separated and quantified. These results show that losses due to shock waves vary with blowing ratio as shock wave strength changes. Aerodynamic loss magnitudes due to mixing vary significantly with film cooling hole geometry, blowing ratio, Mach number ratio, and (in some situations) density ratio. Integrated mixing losses from round cylindrical holes are three times higher than from conical diffused holes, when compared at the same blowing ratio. Such differences depend upon mixing losses just downstream of the airfoil, as well as turbulent diffusion of streamwise momentum normal to the airfoil symmetry plane. [S0889-504X(00)02202-9]
Notch-Strengthening Phenomenon Under Creep-Fatigue Loading Conditions
Authors: Merah N.
Published: July 2002

A study of the notch and frequency effects on fatigue life at high temperature is carried out using notched and unnotched plate specimens of SS 304 under stress-controlled testing conditions. Analysis of the σ-Nf results obtained at 600°C under fatigue and creep-fatigue conditions allowed the generalization of the σ-Nf-Kt relation proposed in an earlier study. Examinations of the experimental data with hold-time testing suggested that in these conditions, the frequency effect should be incorporated in the relationship. Results obtained from the modified relation are in agreement with the experimental data, within a factor of two. Finite element analysis was carried out to determine the state of stresses and strains at the notch root by simulating four creep-fatigue cycles. The computed results indicated that, under zero-to-tension cyclic loading with controlled nominal stress, the maximum local stress at the notch root relaxes; this results in a minimum local stress in compression, and as a consequence, the mean local stress is significantly reduced. The stress relaxation as well as the creep strain accumulation were found to occur only in the vicinity of the notch (within 0.75 mm). The numerical results concerning the local stress relaxation and the time-dependent strain accumulation are used to explain the notch-strengthening effect on life observed in the present study. [S0094-9930(00)00401-7]
Effect of Loading Rate on Fracture Toughness of Pressure Vessel Steels
Authors: Yoon K. K. , Van Der Sluys W. A. , Hour K.
Published: July 2002

The master curve method has recently been developed to determine fracture toughness in the brittle-to-ductile transition range. This method was successfully applied to numerous fracture toughness data sets of pressure vessel steels. Joyce (Joyce, J. A., 1997, “On the Utilization of High Rate Charpy Test Results and the Master Curve to Obtain Accurate Lower Bound Toughness Predictions in the Ductile-to-Brittle Transition, Small Specimen Test Techniques,” Small Specimens Test Technique, ASTM STP 1329, W. R. Corwin, S. T. Rosinski, and E. Van Walle, eds., ASTM, West Conshohocken, PA) applied this method to high loading rate fracture toughness data for SA-515 steel and showed the applicability of this approach to dynamic fracture toughness data. In order to investigate the shift in fracture toughness from static to dynamic data, B&W Owners Group tested five weld materials typically used in reactor vessel fabrication in both static and dynamic loading. The results were analyzed using ASTM Standard E 1921 (ASTM, 1998, Standard E 1921-97, “Standard Test Method for the Determination of Reference Temperature, T0, for Ferritic Steels in the Transition Range,” 1998 Annual Book of ASTM Standards, 03.01, American Society for Testing and Materials, West Conshohocken, PA). This paper presents the data and the resulting reference temperature shifts in the master curves from static to high loading rate fracture toughness data. This shift in the toughness curve with the loading rate selected in this test program and from the literature is compared with the shift between KIc and KIa curves in ASME Boiler and Pressure Vessel Code. In addition, data from the B&W Owners Group test of IAEA JRQ material and dynamic fracture toughness data from the Pressure Vessel Research Council (PVRC) database (Van Der Sluys, W. A., Yoon, K. K., Killian, D. E., and Hall, J. B., 1998, “Fracture Toughness of Ferritic Steels and ASTM Reference Temperature T0,” BAW-2318, Framatome Technologies. Lynchburg, VA) are also presented. It is concluded that the master curve shift due to loading rate can be addressed with the shift between the current ASME Code KIc and KIa curves. [S0094-9930(00)01302-0]
Fabrication of ZnO-doped Zr0.8Sn0.2TiO4 thin films by radio frequency magnetron sputtering
Authors: Huang Cheng-Liang , Hsu Cheng-Shing
Published: July 2002

(Zr 0.8 Sn 0.2 )TiO 4 (ZST) thin films with 1 wt % ZnO addition were fabricated on n-type (100) Si substrates by reactive rf magnetron sputtering at various Ar/O2 mixing ratios (80/20, 90/10), substrate temperatures (300, 350, and 400 °C), and sputtering times (from 2–4 h). The powder target composition of (Zr0.8Sn0.2)TiO4 was synthesized in the experiment. The structure of the films on Si was determined by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The deposition rate increases with increasing Ar concentration and substrate temperature. Moreover, the higher O2 content increases the surface roughness of the deposited films. From observing the cross section and the surface morphology, ZST thin films exhibit a columnar structure. The grain size of the film increased with an increase in the substrate temperature and sputtering time and with a decrease in the oxygen partial pressure. A dielectric constant of 28 (f=10 MHz) and a resistivity of 2.1×109 Ω m were obtained for the ZST thin films in the experiment.
Structure and mechanical properties of thick Fe, Fe–NbC, Fe–Ni–NbC condensates
Authors: Movchan B. A. , Demchishin A. V. , Kooluck L. D.
Published: July 2002

Structure and mechanical properties of pure iron 0.8–2.0-mm thick condensates in tension are studied as a function of the substrate temperature within the range 270 °–860 °C. The mechanical properties of two-phase Fe–NbC condensates, containing up to 18% by volume niobium carbide were investigated at room temperature and 700 °C. The introduction of niobium carbide, having negligible solubility in iron, into the latter permits one to increase the tensile and yield strengths of condensates up to 90 and 86 kg/mm2, respectively, at room temperature, and tensile and yield strengths of 45 and 36 kg/mm2 at 700 °C with 13%–16% by volume NbC content. The effect of alloying the iron matrix with nickel in the amount of 18% by weight on the structure and mechanical properties in tension of Fe–Ni–NbC material was determined. The tensile and yield strengths of such materials reached 116 and 108 kg/mm2, respectively, at 20 °C and 59 and 40 kg/mm2 at 700 °C where the NbC content was approximately 9% by volume. An attempt was made to evaluate the increment of yield strength when introducing NbC-dispersed particles from the stand point of Orowan and Ansell–Lenel theories. It has been found that the contribution of the dispersed particles and solid solution into the condensate, strengthening at room temperature, is governed by the law of additivity.
Quantitative comparison of Ti and TiO surfaces using Auger electron and soft x-ray appearance potential spectroscopies
Authors: Grant J. T. , Haas T. W. , Houston J. E.
Published: July 2002

Integration techniques have been used to obtain the relative surface concentrations of Ti in Ti metal and TiO and between Ti and O in the oxide by Auger electron and soft x-ray appearance potential spectroscopies. It is shown that the use of peak-to-peak signal strengths in derivative data as a measure of relative concentration can give erroneous results due to differences in the line shapes of the various features. This sensitivity to the details of the spectral shapes is shown to be essentially eliminated in data corresponding to the integrals of the derivative spectra. The AES values thus obtained are in good agreement with those to be expected for Ti and TiO and the agreement between the values obtained by the two techniques is shown to be considerably improved.
Surface structure analysis by ion scattering
Authors: Brongersma H. H.
Published: July 2002

When ions collide with the surface of a solid, they may scatter back into the vacuum after one or more collisions with surface atoms. By careful selection of the experimental conditions, it is often possible to separate effectively the singly, doubly, and multiply scattered ions. Since the energy of the scattered ions depends not only on the incident energy and the total scattering angle but also on the identities and positions of the collision partners, information is obtained on both the composition and the short-range structure of the surface. In many cases, additional techniques are useful for the characterization of the surface. Therefore, other diagnostic tools such as low-energy electron diffraction (LEED), secondary-ion mass spectrometry (SIMS) and Auger spectroscopy have been incorporated into our equipment. Applications of primarily ion scattering are demonstrated for a few adsorption processes and for the polar faces of a few semiconductors.
Electronic structure and mechanical properties of hard coatings from the chromium–tungsten nitride system
Authors: Hones P. , Diserens M. , Sanjinés R. , Lévy F.
Published: July 2002

Cr 1−x W x N y films were deposited on silicon by rf reactive magnetron sputtering. The phase and texture were determined by x-ray diffraction analysis. All the films crystallize in the fcc phase. Scanning tunneling microscopy revealed a finely grained surface morphology. The grain size decreases with increasing tungsten content in the films. Quantitative values can be assigned to morphology differences through the measurement of the optical reflectivity. Hardness values obtained by nanoindentation, and the packing density significantly increase upon addition of a small percentage of W to CrN. The electronic structure was analyzed using x-ray photoelectron spectroscopy. As deduced from core level binding energy values (chemical shifts), the W2N and Cr1−xWxN films are more covalent than binary CrN. The higher hardness values in W2N and Cr1−xWxN compounds compared to that of CrN are related to their prominent covalent bonding character between the metal and nitrogen ions.
HBr concentration and temperature measurements in a plasma etch reactor using diode laser absorption spectroscopy
Authors: Chou Shang-I , Baer Douglas S. , Hanson Ronald K. , Collison Wenli Z. , Ni Tom Q.
Published: July 2002

In situ measurements of HBr concentrations and rotational temperatures were recorded in a 300 mm planar inductively coupled plasma (ICP) etch reactor using diode laser wavelength modulation spectroscopy. A pair of diode lasers operating near 1.95 and 2.00 μm were wavelength tuned over the R(7) and P(2) transitions of HBr (2–0 band), time-division multiplexed, and directed through an industrial wafer etch reactor. The rotational temperature (typically 435±8 K) was determined from the ratio of peak absorption signals and the HBr concentration was determined from the measured temperature and absorbance from a single line. The measured rotational temperature in the plasma was relatively independent of conditions studied. The estimated HBr dissociation fraction ranged from 25%–60%, depending on the ICP power applied, gas flow rate, and chamber pressure. Decreases in HBr concentration were detected 1 cm above the wafer surface during blank silicon wafer etching. The HBr dissociation fractions were measured before and after SF6 plasma clean with various focus rings made of quartz, alumina, and silicon carbide. The HBr dissociation fraction increased 17% with the quartz focus ring after the chamber was seasoned. The silicon carbide focus ring had essentially no influence on HBr concentration before and after chamber clean. The success of this work demonstrates the potential of diode lasers for in situ monitoring of the plasma etch process for real time control applications.
Electron temperature measurement in a slot antenna 2.45 GHz microwave plasma source
Authors: Cotrino J. , Palmero A. , Rico V. , Barranco A. , Espinós J. P. , González-Elipe A. R.
Published: July 2002

The electron temperature in a low-pressure microwave electron cyclotron resonance slot antenna produced plasma is obtained. The upper excited atomic level populations have been measured through atomic emission spectroscopy. It has been shown that the Corona balance provides a good description of such levels and, based on this fact, a simple argon collisional-radiative model has been used in the temperature determination.
Growth and structure of aligned B–C–N nanotubes
Authors: Yu J. , Zhang Q. , Ahn J. , Yoon S. F. , Rusli  , Gan B. , Chew K. , Tan K. H. , Bai X. D. , Wang E. G.
Published: July 2002

Aligned B–C–N nanotubes were prepared by bias assisted hot filament chemical vapor deposition from source gases of H2, N2, CH4, and B2H6. Various morphologies were obtained at different growth conditions. The area density of the nanotubes increases with increasing discharge current. The nanotubes grow along the direction of the electrical field. Dense and highly oriented B–C–N nanotubes were obtained at 620 °C and high discharge current. The growth temperature has effects on the tube diameter and the nanotubes grown at higher temperature are thinner than that at lower temperature. The B concentration of the deposits increases with increasing the B2H6 concentration in gas mixture and various B:C:N ratios of 10:81:9, 16:73:11, and 34:42:24 were obtained at different gas composition.
Diffusion of TiN into aluminum films measured by soft x-ray spectroscopy and Rutherford backscattering spectroscopy
Authors: Schuler T. M. , Ederer D. L. , Ruzycki N. , Glass G. , Hollerman W. A. , Moewes A. , Kuhn M. , Callcott T. A.
Published: July 2002

Understanding the atomic bonding properties at the interface between thin films is crucial to a number of key modern technical devices, including semiconductor integrated circuits, magnetic recording media, batteries, and even solar cells. Semiconducting materials such as titanium nitride (TiNx) are widely used in the manufacturing of modern electronic devices, requiring a wealth of information about its electronic structure. We present data from soft x-ray emission, soft x-ray absorption, and Rutherford backscattering spectroscopy experiments involving a sample consisting of a 40 nm TiN layer on top of an aluminum film 600 nm thick. Soft x-ray emission spectroscopy and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy are tools that provide a nondestructive, atomic site-specific probe of the interface, where the electronic structure of the material can be mapped out element by element. Rutherford backscattering spectroscopy (RBS) measurements supply data on the elemental composition and depth profiling of the sample. From these measurements, we show that the Ti and the N diffuse into the Al film to form an equivalent material depth of about 4.5 nm, and the NEXAF structure reveals that the nitrogen has probably formed AlN, and the Ti has also diffused to form a titanium–aluminum compound.
Substrate temperature studies of SrBi2(Ta1−xNbx)2O9 grown by pulsed laser ablation deposition
Authors: Tay S. T. , Huan C. H. A. , Wee A. T. S. , Liu R. , Goh W. C. , Ong C. K. , Chen G. S.
Published: July 2002

Ferroelectric SrBi2(Ta1−xNbx)2O9 (SBNT) thin films were deposited on Pt/TiOx/SiO2/Si substrates at various substrate temperatures by the pulsed laser ablation deposition method. X-ray diffraction shows that the film has a fluorite structure at a substrate temperature of 500 °C. The fluorite structure was transformed into perovskite phase at 550 °C and was fully crystallized at temperatures ⩾700 °C, with a secondary phase present. Secondary ion mass spectroscopy and x-ray photoelectron spectroscopy studies reveal that the secondary phase was a nonferroelectric Bi-deficient pyrochlore phase at the SBNT/Pt interface and the film surface. The pyrochlore structure has a detrimental effect on the ferroelectric properties (i.e., the remanent polarization, coercive field, leakage current and fatigue) of the film. The remanent polarization and coercive field for the film grown at a substrate temperature of 700 °C were 4.79 μC/cm2 and 68.68 kV/cm, respectively, with leakage current <10−7 A/cm2 even at an applied voltage of 8 V and 30% degradation in endurance against fatigue after 2×1012 switching cycles.
Etch depth control in bulk GaAs using patterning and real time spectroscopic ellipsometry
Authors: Cho Sang-Jun , Snyder P. G. , Herzinger C. M. , Johs B.
Published: July 2002

Real time spectroscopic ellipsometry (RTSE) was used to monitor and control the depth of etching into a bulk GaAs wafer. Lateral interference due to patterning is the mechanism by which this optical technique, normally used for thin film measurement, can determine etch depth into bulk material. Scalar analysis permits fast data fitting and real time control. GaAs wafers were patterned with photoresist in line or square patterns with periods of 10, 20, or 40 μm, and etched in a solution of citric acid–hydrogen peroxide–de-ionized water. RTSE data were collected and simultaneously analyzed for etch depth. When the depth reached a preselected target value of up to 1.6 μm the etch was stopped. Final etch depth as measured by scanning electron microscopy was always within 5% of the target depth. Ex situ spectroscopic ellipsometry analysis of the etched GaAs, with the photoresist removed, also agreed well with the RTSE results.
Spreading resistance roadmap towards and beyond the 70 nm technology node
Authors: Vandervorst Wilfried , Clarysse Trudo , Eyben Pierre
Published: July 2002

The manufacturing of deep submicron devices requires the formation of very shallow, highly doped source/drain profiles. Besides the need to determine the correct atomic dopant distribution (using secondary ion mass spectrometry), there is an increasing demand for the accurate determination of the electrical carrier profiles related with the need to monitor the activation of the dopants under reduced thermal budgets. Conventional spreading resistance probe (SRP) has been widely used for this application due to its capability to measure the resistivity (and carrier) depth distribution in Si with a high geometrical resolution (nm) and high dynamic range (nine orders of magnitude). Unfortunately with the application towards very shallow profiles (junction depths less than 35 nm), the concurrent electrical resolution is influenced by several artifacts such as carrier spilling, surface damage, probe penetration, three-dimensional (3D)-current spreading, increasing correction factors, etc. From the spreading resistance roadmap presented it follows that for future sub-100 nm technologies using sub-35 nm junctions, conventional SRP is reaching its limits. As the main limitations arise from the large correction factors (in excess of 2–3000) due to the large contact size and probe separation, large bevel stepsize and probe penetration, a solution is proposed, the Nanoprofiler™ (NP), which is based on a two probe version of the scanning spreading resistance microscopy SRRM technology (small 10–20 nm tips, low force, simultaneous topography measurement), thereby reducing correction factors back to <10 with minimal probe penetration and extremely small stepsize. Theoretically, profiling with 0.1–0.2 nm resolution should be feasible. In view of the complexity of controlling two independent cantilevers, we will discuss the need for them on the basis of the required correction factor size and the impact of lateral (3D)-current spreading and surface damage. Some of the intrinsic capabilities of the NP concept will be illustrated by experimental resistance data measured between a single SSRM tip and TiW–Au surface stripe contact at close separation.
Methods for modeling microwave plasma system stability
Authors: Rummel Paul , Grotjohn Timothy A.
Published: July 2002

Today’s modern commercial semiconductor plasma processes require, more than ever, stable and repeatable energy delivery. One of the challenges to utilizing microwaves for plasma processing is an inherent instability that sometimes renders “repeatable energy delivery” difficult to achieve. This instability often manifests itself as a propensity for the plasma to extinguish or rapidly change to a lower density as system components are adjusted to facilitate optimal energy transfer from the microwave generator to the plasma. This article presents two modeling methods for demonstrating microwave powered plasma system stability, both based on simple plasma system component mathematical models. Each component of a microwave plasma system was first represented with simple equations. These individual plasma system component equations were combined into a single closed-loop ‘plasma system’ Matlab Simulink model. Simulation output was compared directly against actual measured operating parameters of a microwave cavity plasma reactor (MCPR). The individual plasma system component equations were also combined into a single differential “system” equation or “state” equation. This state equation was then tested with a graphical method to further illustrate characteristics of system stability. The Simulink model and the graphical control analysis clearly demonstrated major trends of actual MCPR stability performance, showing the extent to which the actual system could be perturbed before stability was lost, and that the observed instabilities appear to be primarily caused by first order effects of system component interactions.
Debris reduction for copper and diamond-like carbon thin films produced by magnetically guided pulsed laser deposition
Authors: Tsui Y. Y. , Minami H. , Vick D. , Fedosejevs R.
Published: July 2002

The effectiveness of debris reduction using magnetically guided pulsed laser deposition (MGPLD) is reported here. KrF laser pulses (248 nm) of 100 mJ energy were focused to intensities of 6×109 W/cm2 onto the surface of a copper or a carbon source target and a magnetic field of 0.3 T as used to steer the plasma around a curved arc of 0.5 m length to the deposition substrate. Debris counts were compared for films produced by the MGPLD and conventional PLD (nonguided) techniques. A significant reduction in particulates of size greater than 0.1 μm was achieved using MGPLD. For the copper films, particulate count was reduced from 150 000 particles/cm2/nm to 50 particulates/cm2/nm and for diamond-like carbon thin films particulate count was reduced from 25 000 particles/cm2/nm to 1200 particles/cm2/nm.
Charging-damage-free and precise dielectric etching in pulsed C2F4/CF3I plasma
Authors: Ohtake H. , Samukawa S.
Published: July 2002

Charging-damage-free φ0.05 μm SiO2 contact etching in a pulsed C2F4/CF3I plasma has been successfully done. The SiO2 etching rate in C2F4/CF3I pulsed plasma did not decrease even for the pulse-OFF time of 20 μs. The C2F4/CF3I pulsed plasma generated a large amount of negative ions when the pulse-OFF time was increased. These results suggest that these negative ions would enhance SiO2 etching in the pulsed C2F4/CF3I plasma. Under these conditions, the φ0.05 μm SiO2 contact etching in the pulsed C2F4/CF3I plasma was observed as in the continuous plasma etching method. Additionally, the charging damage was drastically decreased in the pulsed C2F4/CF3I plasma because the negative ions in the pulsed C2F4/CF3I plasma reduced the accumulating charge on the substrate. These results imply that the negative ions generated in C2F4/CF3I plasma are very effective for charge-free and precise SiO2 etching.
Preparation and Properties of Reactively Sputtered Silicon Nitride
Authors: Janus Alan R. , Shirn George A.
Published: July 2002

Transparent, adherent, amorphous silicon nitride films in the thickness range of 300 to 15000 Å were deposited on a variety of substrate materials by the reactive sputtering technique. The supported glow-discharge approach was found to be superior to glow-discharge sputtering for the preparation of a uniform, stoichiometric film. Electrical, optical, and chemical properties of the film reflect a density that is less than that reported for the bulk nitride.
Thick semiconductor films for photothermal solar energy conversion
Authors: Hahn R. E. , Seraphin B. O.
Published: July 2002

Efficient and economical photothermal conversion of solar energy requires the use of spectrally selective surfaces for collection and retention of incident solar flux. This spectral selectivity can be obtained from an absorber–reflector tandem by overcoating an opaque metal film having high infrared reflectance with a thick film (1–5μm) of semiconductor having an appropriate band gap. The practical implementation of this design using films of silver and silicon on a variety of substrate materials is described. Chemical vapor deposition (CVD) is used for depositing the absorber and the antireflection layers. The spectral reflectance of coated samples has been measured at temperatures up to 500 °C and gives α/ε values in the range of 12–15, with a solar absorptance of 75%. The solar absorptance increases with temperature, while the thermal emittance typically increases by 2%–4% at 500 °C. Both the film adhesion and the spectral reflectance have remained stable after over 2000 cycles to 450 °C.
Vacuum and wall problems in precursor reactor tokamaks
Authors: Cohen S. A.
Published: July 2002

The Princeton Large Torus (PLT) will be completed in 1975 and two other CTR-oriented toroidal plasma devices, the Poloidal Divertor Experiment (PDX) and the Tokamak Fusion Test Reactor (TFTR), are planned to be completed in 1977 and 1981. The vacuum systems of these machines must satisfy stringent requirements because of unusual operating conditions, such as, magnetic-field-induced strains and eddy currents, energetic particle and photon bombardment, large transient gas loads, and the use of 100 Ci quantities of tritium. In addition, novel vacuum wall surfaces and fast moving mechanical or magnetic plasma limiters will be required to minimize the influx of impurities during discharges.
Synchrotron radiation studies of electronic structure and surface chemistry of GaAs, GaSb, and InP
Authors: Spicer W. E. , Lindau I. , Gregory P. E. , Garner C. M. , Pianetta P. , Chye P. W.
Published: July 2002

The oxidation properties of GaAs(110), GaSb(110), and InP(110) have been studied with the photoemission technique using synchrotron radiation. One part of the work consisted of an investigation of the chemical shifts in the core levels upon adsorption of oxygen in submonolayer quantities. For GaAs and InP, oxygen removed electrons preferentially from the surface column V elements (As and P), leaving the column III elements (Ga and In) unaffected; whereas, for GaSb, both constitutents were involved in the oxidation suggesting a breaking of bonds between the surface atoms and the rest of the crystal. The second part of the study consisted of a careful investigation of the Fermi level (Ef) pinning in the GaAs(110) surface. Three different samples and many cleaves were studied. For one sample, Ef was always at the bulk position. On the other two crystals, both pinned and unpinned cases were found on various cleaves. The unpinned samples had sharp electron distribution curves (EDC’s), while the pinned samples had smeared EDC’s which became sharp for exposures as small as 10 L (1 L=10−6 Torr sec) O2. This, coupled with partial yield spectra showing little change up to 105 L O2, implied that the pinnings on the cleaved surface were due to extrinsic states and that the empty surface states were located in the conduction band. All samples showed pinning at midgap after an exposure of 104 L O2(<1% monolayer). Large changes in the valence band upon oxidation also indicate the possibility of surface resonances in the region 1 to 2 eV below the valence band maximum.
Crystallization of amorphous Si films formed by chemical vapor deposition
Authors: Nagasima Naoyuki , Kubota Nagiko
Published: July 2002

The crystallization process of chemically vapor deposited (CVD) amorphous Si films was studied by using a differential scanning calorimeter. A sharp exothermic peak due to amorphous–polycrystalline transition was obtained in the 665–700 °C range. The crystallization temperature was determined to be 665 °C. Transmission-electron diffraction and transmission-electron microscopic examinations revealed that, when amorphous Si film is heated at a slightly higher temperature than the crystallization temperature, the Si dendrite grains nucleate, and grow in size with heating time.
Rate and pressure dependence of contaminants in vacuum-deposited aluminum films
Authors: Springer R. W. , Catlett D. S.
Published: July 2002

Experiments have been conducted to measure the quantity of trapped impurities in electron-beam-deposited aluminum films. The depositions were conducted at the 1.3×10−4–1.3×10−2 Pa pressure range with rates varying from a few tenths to 7.0 nm/s. An RGA was used to record the residual gas spectrum before and during all runs. The films were analyzed by sputter profiling and Auger electron spectroscopy. The chief contaminants found were carbon and oxygen. The carbon contaminant tracked the gauge pressure over two orders of magnitude ranging from a few atomic percent to the 500–1000 ppm range. The partial pressures of H2O, O2, and other gases were varied during deposition to determine their individual roles in contaminating the films. As a result, a relationship between the residual gas spectrum, and chemical analysis was found.
Oxygen uptake on an epitaxial PbSnTe(111) surface
Authors: Sun T. S. , Buchner S. P. , Byer N. E. , Chen J. M.
Published: July 2002

The oxygen uptake of a molecular-beam-epitaxial Pb0.8Sn0.2Te(111) surface has been investigated by AES, XPS, and UPS studies. The results indicate a strong affiliation of oxygen with Sn ions. Oxidation of Sn starts at an exposure of 104 L, whereas oxidation of Pb and Te starts at an exposure of 106 L. Evidence indicates that Sn ions diffuse from the bulk to the surface in the process of oxygen chemisorption. A sharp increase of oxygen uptake is observed at an exposure of 106 L. It marks the commencement of the oxidation process in which bonds between the surface constituents break in favor of individual affiliation with oxygen. A comparison of these results with those previously obtained for PbTe will be discussed.