bluuebunny/crossref_metadata_2025 huggingface dataset:
Cl
2
-based dry etching of GaN films under inductively coupled plasma conditions
Authors: Im Y. H. , Park J. S. , Hahn Y. B. , Nahm K. S. , Lee Y-.S. , Cho B. C. , Lim K. Y. , Lee H. J. , Pearton S. J.
Published: July 2002

Dry etching of undoped, n- and p-type GaN films was carried out in Cl2-based inductively coupled plasmas (ICPs) using different rf excitation frequencies of 100 kHz and 13.56 MHz, in which the rf chuck power source operates. The etch rates with lower frequency of 100 kHz are somewhat greater than those with a higher frequency of 13.56 MHz due to higher ion bombarding energy with lower frequency. The highest etch rates with the 100 kHz frequency were obtained at moderately high ICP power of 700 W: ∼9300 Å/min of n-GaN, ∼5300 Å/min of p-GaN, and ∼7100 Å/min of undoped GaN. The 13.56 MHz frequency of rf chuck power source produced maximum etch rates of ∼7900 Å/min of n-GaN, ∼5800 Å/min of p-GaN, and 6100 Å/min of undoped GaN at 20 mTorr, 700 W ICP, and 150 W rf power. The surface roughness was relatively independent of the chuck power up to 150 W in 13.56 MHz and showed fairly smooth morphology (rms 1.1–1.3 nm), while etching at higher rf power (>200 W) produced rougher surface.
Investigation of the electron emission from pores in a diamond porous membrane
Authors: Mammana V. P. , Anders S. , Monteiro O. R. , Salvadori M. C.
Published: July 2002

It was previously proposed that porous diamond membranes can be used as field emission arrays. As main features of such a device, we identified a field enhancement factor equivalent or superior to that of a metal edge emitter, allied to a higher vacuum conductance. Emitting membrane prototypes were built and tested. These showed promising emission performance. In this work we continue the membrane pore characterization from a geometric point of view. We also present photoemission electron microscopy images from the emitting area around a pore. These images show that indeed there is enhanced electron emission occurring in that region. Current versus time and current versus field graphs complete the emission characterization.
Effect of oxygen stoichiometry on the ferroelectric property of epitaxial all-oxide La0.7Sr0.3MnO3/Pb(Zr0.52Ti0.48)O3/La0.7Sr0.3MnO3 thin-film capacitors
Authors: Wu Wenbin , Wong K. H. , Mak C. L. , Choy C. L. , Zhang Y. H.
Published: July 2002

Epitaxial all-oxide ferroelectric thin-film capacitors, La0.7Sr0.3MnO3/Pb(Zr0.52Ti0.48)O3/La0.7Sr0.3MnO3 (LSMO/PZT/LSMO), have been grown on LaAlO3(001) substrates by pulsed-laser deposition. By changing the deposition oxygen pressure, we varied the oxygen content in the oxide electrodes and ferroelectric film, respectively, and studied their effect on switching and fatigue behavior of the epitaxial capacitors. The capacitors were also cooled at various oxygen pressures in the range of 5×10−6–10 Torr to examine their tendency to process-induced imprint. It is found that all the capacitors show almost square hysteresis loops with remnant polarization of 35–40 μC/cm2 and a coercive field of 40–50 kV/cm, irrespective of the oxygen concentration in the ferroelectric and electrode films. Contrary to the capacitors using La0.5Sr0.5CoO3 as electrodes, when cooled at reduced oxygen pressures, the LSMO/PZT/LSMO capacitors show a strong resistance to the process-induced imprint failure, which is ascribed to the high thermal stability of the LSMO films. On the other hand, the oxygen content in the electrodes is shown to be an important factor that controls the fatigue behavior of the epitaxial all-oxide ferroelectric capacitors.
Scanning tunneling spectroscopy characterization of As+ implanted InP (100) single crystals
Authors: Ichizli V. , Riemenschneider R. , Hartnagel H. L.
Published: July 2002

Current–voltage measurements performed with a scanning tunneling microscope were carried out on (100)-oriented InP single crystals implanted with As+ ions. I–V investigations were made for InP crystals implanted with two different implantation doses, namely, 6.2×1014 and 6.2×1015 cm−2, and annealed at 400, 500, 600, and 750 °C. First of all, the applicability of the scanning tunneling spectroscopy on an implanted semiconductor with high surface damage is presented. Following this, the damage and recovery processes are analyzed and described on the basis of current–voltage curve variation with implantation dose and annealing temperature change. Some important conclusions are made for behavior and interaction of the host phosphorus and implanted arsenic ions in InP.
SCALPEL aerial image monitoring: Principles and application to space charge
Authors: Gallatin G. M. , Farrow R. C. , Liddle J. A. , Waskiewicz W. K. , Mkrtchyan M. M. , Orphanos P. , Felker J. , Kraus J. , Biddick C. J. , Stanton S. , Novembre A. E. , Blakey M.
Published: July 2002

We present an approach to real time direct aerial image monitoring which utilizes the information contained in an alignment signal generated by scanning the image of a mask grating over a corresponding wafer grating and detecting the backscatter electron signal. The basic principles of this measurement technique are described. The effect of noise and other common errors, such as magnification and rotation on the signal quality, are derived and used to set requirements on signal contrast and noise level for obtaining blur values accurate to approximately 1 nm. The application of this approach to measuring space charge blur is described and preliminary data illustrating the concept is presented. The potential for this technique to form the basis of an automated self-calibration system on SCALPEL tools is clear.
Scanning tunneling microscopy studies of ultrathin gate oxide films grown on highly B-doped Si(100) substrates
Authors: Cai Q. , Hu Y. F. , Hu S. T. , Wang X.
Published: July 2002

In this work ultrahigh-vacuum scanning tunneling microscopy (STM) is used to investigate ultrathin oxide films grown thermally by in situ dry oxidation of clean highly B-doped Si(100) substrates. On a clean starting surface, STM images reveal a special reconstruction induced by boron accumulation. The step structure of the substrate persists and can be recognized on the ultrathin oxide films, indicating layer-by-layer oxidation. The surface roughness is observed to increase upon oxidation, showing what appears in the STM image (at certain bias voltages) as both bright spots and dark holes. These oxidation-induced features also affect the formation of void structures when the oxide films are heated up to 700–750 °C. At the early stage of oxidation on the clean substrates, it is found that boron-induced reconstruction may have an effect on the formation of missing-dimer defects.
Enhanced magneto-optical effect in a GaAs:MnAs nanoscale hybrid structure combined with GaAs/AlAs distributed Bragg reflectors
Authors: Shimizu H. , Miyamura M. , Tanaka M.
Published: July 2002

We present significant enhancement of magneto-optical effect at room temperature in GaAs with MnAs magnetic nanoclusters sandwiched by GaAs/AlAs multilayers acting as distributed Bragg reflectors. The experimentally observed transmissivity and magneto-optical spectra are well explained by theoretical calculations. This new material system will open up the possibility of realizing nonreciprocal magneto-optical devices integrated with semiconductor optoelectronic devices and circuits.
Ferromagnetic MnAs grown on GaAs(001): In situ investigations
Authors: Kästner M. , Schippan F. , Schützendübe P. , Däweritz L. , Ploog K.
Published: July 2002

We have grown ferromagnetic α-MnAs layers on GaAs(001) by molecular beam epitaxy. The surface was studied during growth by reflection high-energy electron diffraction (RHEED) and reflectance difference spectroscopy (RDS) and after growth by in situ scanning tunneling microscopy (STM). During nucleation on the c(4×4) reconstructed GaAs(001) surface the RHEED pattern disappears. STM images at this stage show well defined steps and flat terraces, but a disordered structure on the terraces. After deposition of 1.5 ML MnAs small three-dimensional clusters have been observed by STM. For thicker layers several phases of the MnAs(1̄100) surface with different reconstructions have been observed by RHEED. Intensity oscillations of the specular spot have been found for As-rich growth at 265 °C substrate temperature and deposition rates of 0.2–0.65 ML/s. For temperatures below 360 °C a feature was found in the RD spectra that is sensitive to the surface reconstruction. At higher temperatures the RD spectra did not depend on the surface structure. The (1×2) and (1×1) reconstructions have been cooled down to room temperature. Atomic scale images of these surfaces are presented. The images of the (1×2) structure show asymmetric protrusions, consequently this structure has only onefold symmetry. This leads to the formation of reconstruction domains with opposite orientations of the unit mesh in adjacent domains. The domain boundaries run along the [0001] direction.
Electron cyclotron resonance plasma etching of InP through-wafer connections at >4 μm/min using Cl2/Ar
Authors: Chen Y. W. , Ooi B. S. , Ng G. I. , Tan C. L.
Published: July 2002

We report the development of very high etch rates (>4 μm/min), for InP via hole processes. These processes were developed in an electron cyclotron resonance system using a Cl2/Ar plasma without heating the sample. The InP etch rates increased as a function of Cl2 percentage in the Cl2/Ar mixture, rf power, or microwave power. Via holes, with depths of 100 μm, suitable for monolithic microwave-integrated circuits applications, have been achieved at etch rates as high as 4 μm/min. To the best of our knowledge, this is the highest etch rate ever reported in InP for via hole applications.
Low temperature inorganic chemical vapor deposition of Ti–Si–N diffusion barrier liners for gigascale copper interconnect applications
Authors: Eisenbraun Eric , Upham Allan , Dash Raj , Zeng Wanxue , Hoefnagels Johann , Lane Sarah , Anjum Dalaver , Dovidenko Katharine , Kaloyeros Alain , Arkles Barry , Sullivan John J.
Published: July 2002

A new low temperature inorganic thermal chemical vapor deposition process has been developed for the growth of titanium–silicon–nitride (Ti–Si–N) liners for diffusion barrier applications in ultralarge scale integration copper interconnect schemes. This process employs the thermal reaction of tetraiodotitanium (TiI4), tetraiodosilane (SiI4), and ammonia (NH3) as, respectively, the individual Ti, Si, and N sources. Ti–Si–N films were successfully grown over a broad range of deposition conditions, including wafer temperature, process pressure, and TiI4, SiI4, and NH3 flows ranging, respectively, from 350 to 430 °C, 0.1–1 Torr, and 2.5–8.0, 2.5–12.5, and 100–250 sccm. Film stoichiometry was tightly tailored through independent control of the Ti, Si, and N source flows. Film properties were characterized by x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, transmission electron microscopy, scanning electron microscopy, x-ray diffraction, and four-point resistivity probe. Resulting findings indicated that the texture and resistivity of the Ti–Si–N system were dependent on composition. In particular, films with a Ti33Si15N51 stoichiometry exhibited a nanocrystalline TiN phase within an amorphous SiN matrix, highly dense morphology, resistivity of ∼800 μΩ cm for 25 nm thick films, and step coverage of ∼50% in 130 nm wide, 10:1 aspect ratio trenches. Oxygen and iodine contaminant levels were below, respectively, 3 and 1.4 at. % each. Preliminary copper diffusion-barrier studies indicated that barrier failure for 25 nm thick Ti34Si23N43 films did not occur until after annealing for 30 min at 700 °C.
Microcomb design and fabrication for high accuracy optical assembly
Authors: Chen Carl G. , Heilmann Ralf K. , Konkola Paul T. , Mongrard Olivier , Monnelly Glen P. , Schattenburg Mark L.
Published: July 2002

There are two popular optic designs for x-ray space telescopes: the traditional monolithic design, which has demonstrated subarcsecond resolution but at enormous weight and cost per collecting area, and the foil design, which has achieved far greater collecting area per weight and cost, but with resolution limited to the arcminute level, in part due to foil assembly inaccuracy. In this article, we present the design and the fabrication of a novel micromechanical device, the so-called microcomb, which is used to assemble high-accuracy foil x-ray optics. To achieve submicron foil alignment accuracy, two types of microcombs have been fabricated via microelectromechanical systems technology. Reference combs provide highly accurate single-point contacts against which foils are registered, and spring combs provide the mechanical actuation needed to properly position and shape the foils. Briefly, we introduce some basic concepts regarding grazing-incidence x-ray optics. We then present a theoretical model that has given rise to the unique shape of the spring microcomb. Finally, the fabrication process used to produce the microcombs is discussed.
Transport Properties of Electrons in Inverted InSb Surface
Authors: Komatsubara K. F. , Katayama Y. , Kotera N. , Kobayashi T.
Published: July 2002

Measurements were made of electrical transport properties of the electrons in inversion layers produced in metal–oxide–p-InSb structure at 4.2 K. One possible interpretation is reported. Surface conductance Δσs due to inversion layers as a function of gate voltage VG was measured in magnetic field H up to 14 kOe. The curves of Δσs in the magnetic field normal to the surface had plateaus. The width of the plateaus were enlarged on the positive side of VG with increasing magnetic field. While Δσs in the magnetic field normal to the surface decreased ordinarily with increasing H, Δσs in the field parallel to the surface plane tended to a finite value. Values of Δσs showed two peaks when the direction of the magnetic field was rotated in a plane normal to the surface current. The width of the peak was narrower in the case of magnetic fields where electrons were pushed toward the oxide–InSb interface rather than into the bulk of the InSb. These characteristics may be interpreted as follows: The effect of quantization of electron motion in the inversion layer becomes clearer in the behavior of Δσs with the aid of a magnetic field which quantizes the motion of electrons in planes parallel to surface. The peculiar dependence of Δσs on the direction of the magnetic field is thought to originate in the different mechanisms of electron scattering on both sides of the inversion layers mentioned above.
Preparation and Characteristics of Thin Films of Nickel Zinc Ferrite
Authors: Hellicar N. J. , Young A. , Biggers J. V.
Published: July 2002

Thin films of nickel zinc ferrite have been prepared by rf sputtering, onto alumina substrates, at various temperatures. Measurement of remnant magnetisation combined with x-ray spectrographic data, enabled us to optimize conditions for the preparation of reproducible films. Chemical stoichiometry of the films was checked by x-ray probe analysis on a low-angle polished section of a film and by atomic absorption spectrometry on solutions of films in hydrochloric acid. The development of spinel phases in the films was followed using a high temperature x-ray camera. The existence of a wustite phase at the substrate film interface of films deposited onto “cold” substrates suggests that the material is transferred from the target as individual atoms of iron, nickel, and zinc. Stoichiometry of composition is not reached until considerable pre-sputtering has taken place. Films deposited on to cold substrates are amorphous. Considerable energy is required to recombine the individual oxides into a spinel phase. Structural homogeneity is dependent upon heat treatment. A similarity to bulk ceramic processing is indicated.
Refining and Decarburizing Steel-Degassing Process in the Melting Practice of Alloy Steels
Authors: Bauer H. , Fleischer H. J. , Otto J.
Published: July 2002

Reduction of the oxygen content of low to medium alloy steels by the C–O reaction under low pressure is discussed. Avoidance of disturbing reactions with the ladle refractory is accomplished by using basic lined teeming ladles with sliding stoppers. The exothermic vacuum refining of high chromium content alloyed steels is accomplished with gaseous oxygen. The importance of this new process should be considered when planning for the construction of steel plants in the future.
The Importance of Vacuum and Remelting Practices in a Modern Specialty Steel Plant. Part I: Metallurgical Problems and Their Solution
Authors: Mueller-Aue H. J. , Spitzer H. , Tesche K. , Zingel G.
Published: July 2002

In the production of specialty steels, a number of merallurgical problems are encountered that affect the ultimate quality and cost. To name a few, there are high-cost charging materials, long melting times, inadequate alloy recovery, the need for compliance with extremely close compositional analysis, costly desulfurization, slow precipitation of deoxidizing products, high hydrogen contents, oxygen, nitrogen, and hydrogen pick-up during tapping, and segregation during solidification. Various degassing methods developed, with and without agitation, washed and non-washed baths, are all applied in vacuum decarburizing, deoxidizing, and complemental alloying. It is possible to keep these operations separate from the actual melting plant and adopt a two-stage technique made up of the “melting furnace” and “plant for treatment.” This separation increases capacity substantially and reduces costs. Larger, economical vacuum-induction furnaces permit melting, decarburizing, deoxidizing, alloying, evaporation, and pouring under vacuum or inert gas. Two remelting practices using vacuum and slag have been developed to very high technological standards which permit the application of additional refining and ensure a practically segregation-free solidification.
Deoxidation of Stainless Steel by Carbon in Laboratory-Scale Vacuum Induction Melting
Authors: Watanabe Tetsuya
Published: July 2002

This paper describes an investigation of deoxidation of stainless steels by carbon during laboratory-scale vacuum induction melting. Chemical kinetic processes occurring during deoxidation by carbon, final equilibrium pressure of CO, deoxidation limit, and the effect of SiO2 in refractory materials on deoxidation efficiency, are explained.
Removal of Hydrogen by Pouring Molten Steel in Vacuum
Authors: Fukumoto M. , Taniguchi K.
Published: July 2002

An investigation was made into the removal of hydrogen from the melt of medium carbon steel on 10 heat practices of vacuum, pouring under a pressure of 8–12 mmHg. The degassing process can be divided into three steps according to observation from high-speed photography. By vacuum degassing, hydrogen, nitrogen, and oxygen are reduced from an average of 3.5 to 1.7 ppm, from 70 to 60 ppm, and from 60 to 35 ppm, respectively. With the composition and the volume of purge gas which comes out of the steel in the vacuum tank, hydrogen, nitrogen, and oxygen in the melt should decrease by about 2, 9, and 15 ppm, respectively. The removal of hydrogen depends upon the formation and the growth of gas bubbles. In this case, the amount of oxygen has a large affect upon the removal of hydrogen. In other practices, it is recognized that a lower pressure such as 1–3 mmHg is more favorable for the removal of hydrogen than 8–12 mmHg from the view point of growth and formation of gas bubbles.
Design and Operation of a One-Chamber Vacuum Furnace for Dewax, Presinter, and Sinter of Cemented Carbide
Authors: McCain Walter M.
Published: July 2002

Cemented carbide production is via normal powder metallurgy processes. Cobalt is the most common “cement” and commercial paraffin is the most common pressing lubricant. Production furnaces for processing cemented carbide have evolved from simple hydrogen atmosphere furnaces to complex, specialized, multi-chamber vacuum furnaces. The workhorse of the industry today is semi-batch equipment, carousel-like, in which loads are lowered from a loading chamber onto an indexing table in a large cylindrical vacuum tank, and successively rotated and raised into a dewax furnace, then a sinter furnace, and into cooling, before being finally unloaded from the initial loading chamber. While having excellent capacity per investment dollar or per labor dollar, such equipment lacks process flexibility, and loss of a single component can stop the whole process. In 1964 a single chamber design was conceived, inherently more simple, with good flexibility, and lower incremental investment. A prototype was built and tested in 1965, and by 1966 the first two production furnaces were in operation. Many such furnaces are now in operation, and more are currently being installed. The removal of the pressing lubricant from the reaction zone is critical to the maintenance of the carbon balance required. While its removal is relatively easy in a hydrogen furnace, it is physically more difficult in vacuum. Reference to a Cox chart will permit design of a reasonably efficient system. Each of the seven major chemical and physical reactions which occur in converting the powder metal compact to a fully dense “hard metal” part, must be taken into account in the design of production equipment. Liquid phase sintering consists of densification, homogenization, and controlled grain growth. Equations have been developed expressing grain growth as a time-temperature function. Time-temperature profile surveys have been used to determine isotherms, and isograin growth lines, to provide closely controlled sintering.
Effect of Atomization Media and Consolidation Techniques upon Physical Properties of a P/M Cobalt-Base Alloy
Authors: Brandstedt S. B.
Published: July 2002

Inert gas produces a powder with less surface area and lower gas content than water atomization. Nitrogen as an atomization medium results ia approximately five times the nitrogen content compared to powders atomized with argon. Oxygen is present principally in the form of surface oxide, and to a minor extent as adsorbed gas on the surface of the powder particles. The latter can be removed by a vacuum treatment which also partially removes the oxide film. Results from Coldstream processing with air as the fluid for comminution is compared with inert gas processing. Coldpressing and sintering, hot extrusion, and hot forging are compared as alternative methods to consolidate powder of type X-40 into high density bodies. Densities of 92% of theoretical were obtained by coldpressing and sintering in dry hydrogen or vacuum. Both hot forging and hot extrusion using the canning-evacuation method produce full density compacts. Room temperature properties for X-40 and two other Co-base alloys were determined for these consolidation methods. Metallographic evaluation of P/M products vs conventionally-cast material reveals differences believed to produce improved reproducibility and higher reliability of the P/M product. Alloys earlier known as “nonforgeable” can be given a high degree of forgeability by starting with a prealloyed powder as the raw material. Examples of such applications are presented.
Deconvolution Techniques in Auger Electron Spectroscopy
Authors: Mularie W. M. , Peria W. T.
Published: July 2002

The use of Auger electron spectroscopy (AES) as a tool for the study of band structure or Auger processes in solid has been limited by the lack of resolution resulting from the excitation and measurement methods used in AES. In addition to these instrument broadening effects, it is found that discrete, inelastic interactions of Auger electrons in solid can contribute a structured, low-energy tail which extends several times the main bandwidth. By using the energy-loss and resolution information contained in the nearly elastically backscattered electron distribution in a deconvolution technique, it was found that the effects of instrument broadening and inelastic interactions in the observed Auger electron energy distribution could be significantly reduced, thus yielding higher resolution Auger spectra. Deconvolved spectra were obtained from In and CdS as well as from oxygen adsorbed on several substrates.
Current Flow through Thin Insulating Films: Basic Principles and Device Applications
Authors: Mead Carver A.
Published: July 2002

The fundamental physics underlying current flow through thin insulating films is reviewed, with emphasis placed on those experiments central to the identification of the dominant current flow mechanism in a given structure. Recent data obtained on metal-insulator-metal structures incorporating single crystal thin films represents unambiguous observation of both thermionic emission and tunneling. Device applications of thin films are also summarized.
Scanning Electron Microscope Study of Substrate Surfaces
Authors: Lichtman David
Published: July 2002

The scanning electron microscope (SEM) has been used to study the microstructure of substrates used in surface studies experiments. Wire, ribbon, and samples cut from ingots have been studied in the as-received state, after polishing and cleaning treatments, and after experimentation is completed. Polycrystalline and single crystal samples of materials such as rhenium, tungsten, nickel, etc., have been looked at. In all cases, considerably more microstructure has been found than anticipated. Cleaning processes and vacuum heating produce considerable changes in the surface as can be seen in the photographs obtained at magnifications up to 50 000. The effect of these very nonplaner, nonsimple regions on the adsorption–desorption process and on the theoretical models recently developed for gas–surface interactions is considered.
High-Efficiency High-Temperature Radiation Heat Shields
Authors: Crawford C. K.
Published: July 2002

A new configuration for high-temperature heat shielding has been developed and tested; the shields are several times as efficient as those in common use. The configuration consists of a multiturn, close-spaced spiral, wound out of thin tantalum sheet. Conduction losses around the spiral are negligible. Turn-to-turn spacings down to about 100 μm are maintained using low loss spacers; the conduction loss of the spacers sets the limit on the design. A theory is presented for the design of vacuum heat shielding; fundamental limits are considered. Two applications are a mass spectrometer Knudsen cell generating a neutral carbon atomic beam at 2400 K using a total input power of only 165 W, and a high-temperature direct-vaporization ion source generating a 10−6-A gallium beam with a total input power of only 110 W. An attractive future application might be large high-temperature ovens, where large amounts of power have previously been required.
Adjusting Frequency of Monolithic Crystal Filters with an Automatic Vapor Plater
Authors: Morse W. C. , Rennick R. C.
Published: July 2002

The adjustment of individual resonator frequencies is essential in the process of manufacturing monolithic crystal filters (MCF). This paper will discuss the design and performance of a vapor plating facility for the automatic adjustment of these resonator frequencies in the process of manufacturing eight resonator MCF’s. This facility is designed to adjust eight filters (64 resonators) per pump-down cycle. Design of the pumping system, vacuum chamber, and electronic control system are discussed in detail. This involves the interfacing of an electronic control system with the vacuum station in order to achieve precise positioning and dynamic frequency measurement of the devices being plated, as well as variable plating rate at critical stages of adjustment. The system may be programmed automatically by tape or operated manually.
Bistable Switchable Memory Device
Authors: Jackson G. N.
Published: July 2002

Thin film devices with a simple capacitor geometry were made with evaporated aluminum electrodes and with an rf sputtered lead zirconate dielectric. These devices could be switched from a high resistance state (typically 106 Ω) to a lower resistance state by application of a forward voltage over a certain threshold level. Switching of the devices back to their high resistance state was achieved by application of a reverse “over threshold” voltage. The devices could be read with a forward “under threshold” voltage. Either resistance state was maintained whilst the device was disconnected from external circuitry. Threshold levels were about 2 V. The discovery of this device is used to illustrate the importance of measurement of properties of films deposited in all positions from the center to the edge of the work table in rf sputtering systems.
Auger Line Shape Comparison of N and S in Two Different Chemical Environments
Authors: Sickafus E. N. , Steinrisser F.
Published: July 2002

Line shapes of Auger electron spectra have been analyzed in the derivative mode dN/dE to obtain evidence of chemisorption bond characteristics of sulfur and nitrogen in two different chemical environments. Sulfur in a monolayer surface structure on nickel, Ni(110)–c(2×2)S is characterized as having a residual d-band and two (molecular orbital) resonances, as first depicted by ion-neutralization spectroscopy; while sulfur in a cleaved surface (112¯0) of CdS displays only filled band properties with no resolvable resonance structure. Nitrogen adsorbed on Ni(110) is characterized by a residual d-band and two resonances: one at ∼12 eV and the other at ∼25 eV below the vacuum zero. The analysis is consistent with data published earlier on a characteristic energy-loss description of Ni(110)-(disordered)N. Nitrogen adsorbed on Si(111) appears to have similar resonances at 13 eV and 27 eV below the vacuum zero with no other intervening band structure.
Design and Operation of a Large Scale Semicontinuous Electron Beam Evaporator
Authors: Grubb Albany D.
Published: July 2002

A semicontinuous electron beam evaporator has been designed and built for the application of multilayer films on glass substrates. The evaporator can apply three-layer coatings on substrates ten feet by twelve feet for use as high performance architectural and automotive products. Here we deal with some of the problems encountered in the design, construction, and actual operation of such a semicontinuous evaporator. Reflective glass produced in this system has become a major factor in the design of many new building projects.
Thin Film Manufacturing by Computer Control
Authors: Effron M. S. , Farrow C. H. , Titcomb F. R.
Published: July 2002

In the thin film semiconductor manufacturing field there is an ever increasing effort toward product quality and uniformity. This paper describes the computerized evaporation process for the manufacturing of interconnecting aluminum metallurgy on silicon substrates. An IBM 1800 data acquisition and control system has been programmed to interface with several modified Veeco manufacturing evaporation systems. The function of the 1800 was to completely control the evaporation cycle, record discreet and continuous process data, perform data retrieval, and provide failure recovery mechanisms. The computer-controlled runs are compared statistically to manually controlled runs in this paper for three major process parameters: film thickness, rate of deposition, and alloy concentration (copper percent concentration in the aluminum films).
Energy transfer between electrons and photoresist: Its relation to resolution
Authors: Han Geng , Cerrina Franco
Published: July 2002

In the study of high-energy photon and electron lithography the photoresist has been treated as a uniform and isotropic medium. As dimensions become smaller and exposure fluctuation more noticeable, we cannot ignore the processes that happen at the molecular scale. Hence, it becomes important to understand how the energy is coupled from an exciting radiation to the various molecular components of a photoresist material. In this article, we present the first step in the development of such a model. We base the analysis on the method of virtual quanta for the incoming electron, and use the dielectric function response theory to describe the medium. The results correctly describe the decreasing strength of the interaction on the electron energy, and yield an estimate of ≈2–3 nm for an average interaction distance. A simple Monte Carlo simulation is implemented to verify the effect of the fluctuations due to the virtual quanta on a line edge.
Selective Area Metallization by Electron-Beam Controlled Direct Metallic Deposition
Authors: Ballantyne J. P. , Nixon W. C.
Published: July 2002

Direct metallic deposition exploits the advantages of electron-beam exposure for the production of fine structures and avoids the use of resists and chemical etching. The process involves the electron-induced decomposition of metallic compounds in areas precisely defined by an electron probe. In principle, the resistivity of the deposits formed by direct metallic deposition can be controlled by regulating the amount of molecular dissociation which takes place. To date, in experiments with silver chloride, deposits with submicron dimensions have been obtained. Typical sheet-resistance values of the deposits range from 10 to 1000 Ω/square for exposures varied from 3×10−2 to 5×10−3 C/cm2. A Monte Carlo simulation of electron scattering in thin films on a supporting substrate has shown that the minimum deposit dimensions which can be expected from the process vary directly with film thickness and inversely with accelerating voltage. Experimental evidence is in agreement with the theoretical predictions.
Electron Optics of an Off-Axis Solid-State Light Valve
Authors: Casasent D. , Caimi F.
Published: July 2002

The solid-state light valve, consisting of an off-axis electron gun and an electro-optic target crystal, is used as a two-dimensional spatial light modulator for a collimated laser beam. With a 1 mil electron beam spot and 50 μA beam current, 1000 line resolution and real time operation at TV frame rates have been achieved. The electron optics and three error function figures of merit for a generalized off-axis electron beam system are presented. The component selection procedure and an analog correction preprocessor design on a precalculated basis are discussed.
Study of a Glow Discharge Ion Source
Authors: Flemming J. P.
Published: July 2002

Some properties of a glow discharge source in which boron trifluoride was used as a source feed-gas are described. The source generated a beam with a multipeaked energy spread with width approximately equal to the voltage used to generate the discharge (up to several kilovolts). The energy distributions of different ion species extracted from the source were not all the same and, in particular, the section of the beam taken from an energy band situated a few hundred volts above cathode potential was found to consist essentially of boron ions. Beryllium ions were observed to be generated close to the cathode of the source from atoms sputtered from the extraction canal. The highest total output current of the source was 100 μA.
Potential of Field Emission Cathodes for Microfabrication
Authors: Wardly G. A.
Published: July 2002

For field-emitter tip currents in the range of 100 μA, field-emission guns can compete favorably with thermionic LaB6 guns for microfabrication with 2000 Å working beam diameters. The stable operation of tip currents between 10 and 1000 μA, for periods totalling hundreds of hours, requires an understanding of the steady-state and transient adsorbed gas layer on the emitter surface. This has been accomplished in a simple gun-lens. Furthermore, Boersch effect energy broadening appears to be significantly operative at emission intensities on the order of 10−2 A/sr. The staircase-like current fluctuations indicate quantum events on the emitter surface. In fact, intense emission lobes have been spatially separated by spherical aberration in a large aperture configuration.
LEED from ordered overlayers: A description of the cross section in terms of substrate layer scattering matrices
Authors: Liebsch A.
Published: July 2002

A new method is presented for the description of multiple elastic scattering of low-energy electrons from ordered overlayers adsorbed on periodic substrates. By separating, in the exact multiple-scattering series, the scattering events that occur within the overlayer from those in the substrate, it is possible to treat the geometrical structure of the overlayer independent of the Bravais net of the underlying substrate layers. Consequently, the dynamical scattering cross section is expressed entirely in terms of layer scattering matrices of the substrate, which thereby avoids the more time-consuming sublattice formalism that has been used in previous exact calculations of diffraction intensities.
OSHA and its relation to risk
Authors: Reider Roy
Published: July 2002

Within this generation society has become more aware of risks inherent in technological development. The historic contributions to safety by voluntary consensus standards are evolving into uniform legislated standards, thus extending these gains to more workers than before. The Occupational Safety and Health Act (OSHA) of 1970 was an extraordinarily large, but natural, step in social legislation. It is intended to raise occupational health and safety standards beyond the level achieved under the stimulus of insurance and accident cost penalties. The main thrust of this Act was avoidance of death and serious harm. Despite any misgivings one might have about the bureaucratic process, this Act has built-in provisions for review and appeal which address the relevance of citations to risk. It may be fairly concluded that the adminstration of OSHA has, so far, been concerned with real risk; this conclusion requires some detachment from pettifogging. However, OSHA alone will not produce the level of safety within the reach of enlightened management. Classical safety programs—inspections, training, procedural controls—and strong management interest are still required.
Vacuum arc melting of tungsten-hafnium-carbon alloy
Authors: Ammon R. L. , Buckman R. W.
Published: July 2002

The vacuum arc casting of tungsten alloys, which contain carbon as an alloy addition, require special melting procedures in order to produce melts of consistent controlled levels of alloy content. A melting procedure will be described in which elemental components of a tungsten 0.35% HfC alloy are assembled to form an electrode for ac vacuum arc melting to produce 3-in.-diam ingots. Melting procedures and analytical chemistry are discussed and compared with data for ingots produced by other techniques.
A miniature extractor gauge for the UHV
Authors: Blechschmidt D.
Published: July 2002

The design and performance of a miniaturized hot filament ionization pressure gauge, specially developed for the CERN intersecting storage rings, is described. It is mounted on a standard metal flange with ceramic feedthroughs and fits into an aperture of 15.7 mm. The gauge is of the extractor type and has a sensitivity factor for nitrogen of about 5 Torr−1. Its low pressure limit, about 5×10−12 Torr nitrogen equivalent, is mainly due to x rays. These two characteristic figures have been obtained, in spite of the gauge's smallness, by an optimization of most of the geometrical and electronical parameters. Some problems, seriously affecting the gauge’s performance, and particularly arising from its size, such as space charge effects and thermal outgassing, are discussed.
Carrier distribution profiles in Si-doped layers in GaAs formed by focused ion beam implantation and successive overlayer growth
Authors: Hada Takuo , Goto Takayuki , Yanagisawa Junichi , Wakaya Fujio , Yuba Yoshihiko , Gamo Kenji
Published: July 2002

Selectively doped layers buried in GaAs were formed by low (50 and 200 eV) and high (30 keV) energy focused Si ion implantation and successive overlayer growth using a focused ion beam/molecular beam epitaxy (MBE) combined system to investigate the possibility to form patterned δ-doped layers. Carrier distribution profiles were measured by means of a capacitance–voltage profiling technique at room temperature. It was found for the low-energy implantation that the width of the depth profiles of the carrier distribution decreased with increasing sheet carrier density and was roughly in agreement with a theoretical estimation obtained by solving the Poisson equation. The width was decreased when the sheet carrier density increased by annealing. This indicates that the width is determined by a sheet carrier density and not by Si dopant profiles, and that narrower carrier profiles can be formed by optimizing annealing parameters, although the widths were 2–5 times wider than those observed for the MBE-grown δ-doped GaAs. The same doping efficiency as for the low-energy implantation was achieved but the distribution width was close to that of the dopant distribution.
Real time pattern changing in atomic beam holography using phase shift by Stark effect
Authors: Fujita J. , Mitake S. , Shimizu F.
Published: July 2002

An electrically controlled phase hologram has been used to change the reconstructed atomic image on a solid surface. The second order Stark effect of the laser-cooled metastable Ne atom was used to induce the phase shift during the atoms passage through the hologram. By controlling the applied electric voltage, the reconstructed pattern was switched according to the induced phase shift.
Evaluation of a 100 kV thermal field emission electron-beam nanolithography system
Authors: Tennant D. M. , Fullowan R. , Takemura H. , Isobe M. , Nakagawa Y.
Published: July 2002

We report on the results of performance evaluation tests of a JEOL model JBX-9300FS electron- beam nanolithography system operating at 100 kV. The system was tested in the areas of lithographic resolution, stability, exposure uniformity, and pattern placement accuracy. A minimum spot size of 4 nm was measured at a current of 100 pA. The spot remained below 6.5 nm for beam currents up to 8 nA. Maximum digital to analog converter linearity and deflection amplifier errors were below 0.5 nm. Pattern placement accuracy in a 50 mm square area was found to be within ±16 nm and inside the 500 μm writing field within ±7 nm.
Mechanical properties and pattern collapse of chemically amplified photoresists
Authors: Que Long , Gianchandani Yogesh B.
Published: July 2002

The mechanical properties of positive tone chemically amplified resists UV6 and APEX-E are measured and used in finite element analysis (FEA) to determine the mechanical compliance of photoresist lines as an indicator of the propensity for pattern collapse. Specifically, the residual strain is determined by surface micromachined resist structures; the residual stress, expansion coefficient, and glass transition temperatures are determined from wafer curvature measurements; and the Young’s modulus is calculated from the stress and strain. The results indicate that UV-6 has higher strain and a higher coefficient of thermal expansion than APEX-E. However, it has lower residual stress because its Young’s modulus is 50%–70% lower than that of APEX-E. FEA indicates that lines of UV6 have greater compliance than those of APEX-E, and are more easily deformed by fluidic forces during develop and rinse steps. This is fully consistent with separate reports that demonstrate a greater likelihood of pattern collapse in UV6 than APEX-E.
Generation of arbitrary three dimensional surfaces by x-ray lithography
Authors: Feldman M. , Lee G. S. , Noel D. , Khan Malek C. , Bass R.
Published: July 2002

High aspect ratio microstructure systems with nearly vertical walls are routinely produced by conventional deep x-ray lithography. More complex structures, in which the height is an arbitrary function of position, have many practical applications, for example, as molds for arrays of microscopic optical elements. We have demonstrated a very accurate technique by which such structures may be fabricated by an entirely dry process, using the x-ray ablation of heated Teflon [poly(tetrafluoroethylene)] in an x-ray lithography beamline at the Center for Advanced Microstructures and Devices at Louisiana State University. We observed that the total amount of material ablated is directly proportional to the incident dose. By using a half tone mask, the dose, and hence the amount of material removed, may be accurately controlled at every point on the sample.
Characterization of phase defects in phase shift masks
Authors: Adam Konstantinos , Hotta Shoji , Neureuther Andrew R.
Published: July 2002

Rigorous simulation of electromagnetic scattering and imaging are used to assess the tendency of nonplanar phase defects to print in optical lithography with alternating phase-shifting masks. The ideal model for phase defects, which assumes that the fields are transmitted with unaltered amplitude and a phase shift of 180°, is proven inaccurate through simulation of isolated defects. The brightness and the phase are found to depend strongly not only on their height but on the lateral size as well. Data are also presented on a variety of defect shapes, sizes, heights, positions, and their impact when located near mask features. Linewidth variations due to lines/posts and scratches/holes are typically 30% larger and 50% smaller, respectively, than these predicted from an ideal geometrical mask model.
Roughness study of a positive tone high performance SCALPEL resist
Authors: Ocola L. E. , Orphanos P. A. , Li W.-Y. , Waskiewicz W. , Novembre A. E. , Sato M.
Published: July 2002

In this article we discuss the line edge roughness of positive chemically amplified resists exposed on the SCALPEL exposure system in terms of the image formation process. The image formation process for a SCALPEL exposure on a positive chemically amplified resist has been simulated using discrete models from exposure through development. Key parameters have been identified that enable image formation simulations without the need of detailed molecular models. Molecular models are needed though to obtain several of these parameters. Surface and line edge roughness, as measured by scanning electron microscopy and atomic force microscopy, have been simulated and compared to experimental results. Results are consistent with a “percolation network formation for diffusion-reaction development” model for chemically amplified resists.
Implementation of real-time proximity effect correction in a raster shaped beam tool
Authors: Boegli V. , Johnson L. , Kao H. , Veneklasen L. , Hofmann U. , Finkelstein I. , Stovall S. , Rishton S.
Published: July 2002

A method for real-time backscatter correction has been implemented in a 50 keV raster-scan electron-beam mask exposure system. The real-time nature of the correction makes it an attractive, user transparent feature with flexibility to choose the correction algorithm and scattering parameters. This article describes the correction algorithms and the hardware added to the data path. We compare simulated critical dimension (CD) linearity with results from mask exposures in our new raster shaped beam proof-of-concept tool. Performance meets both throughput and CD linearity requirements for the 130 and 100 nm device generations.
Thermal modeling of a polysilicon-metal test structure used for thermally induced voltage alteration characterization
Authors: Tangyunyong Paiboon , Benson David , Cole Edward I.
Published: July 2002

Thermal modeling and simulations were used to analyze the thermal profiles of a polysilicon-metal test structure generated by localized heating with an infrared laser. Localized laser heating is the basis of a new failure analysis technique, thermally induced voltage alteration (TIVA), that can identify shorted interconnects in integrated circuits. The modeling results show that variations in thermal profiles of the test structure measured by the TIVA technique are due mainly to preferential laser absorption in various locations in the test structure. Differences in oxide thickness also affect the local heat conduction and temperature distribution. Modeling results also show that local variation in heat conduction is less important than the absorbed laser power in determining the local temperatures since our test structure has feature sizes that are small compared to the length over which the heat spreads.