bluuebunny/crossref_metadata_2025 huggingface dataset:
A study on electromagnetron for plasma polymerization
Authors: Yasuda H. , Olcaytug F.
Published: July 2002

Cylindrical electromagnetrons in which electromagnets are integrated within the electrodes so that magnetic strength of magnetron can be adjusted as a parameter of magnetron, are used for plasma polymerization. Basic factors involved in the design and construction of a cylindrical magnetron with multiple electromagnets encased in a nonmagnetic metal case were investigated. An enamel-insulated wire (diameter dw ) is wound on a core cylinder (length L) for the thickness of M. The magnetic fields produced by such a solenoid are calculated as functions of parameters L, M, and dw. Basic characteristics of electromagnets as functions of current and wattage are measured and compared with calculated values. Magnetic field profiles of a single magnet and magnetrons which consist of double magnets arranged in N–S/N–S, and N–S/S–N sequences are measured as functions of current and the distance from the surface of a magnetron. The maximum magnetic flux is proportional to the square root of the wattage, and it was found that approximately 50 W are required to produce 1500 G, regardless of the size of wire used. Glow discharge characteristics and deposition rates of methane were studied for a seven segment magnetron and a continuous magnetron of identical dimensions.
Electron emission characteristics of sputtered lanthanum hexaboride
Authors: Mroczkowski Susan J.
Published: July 2002

Magnetron sputtering was used to deposit a thin film of lanthanum hexaboride for cathode structures. The chemistry of the coatings was studied with x-ray diffraction, Auger electron spectroscopy, and x-ray photoelectron spectroscopy. The work function and electron emission characteristics of the coating have been studied in a diode test cell using tungsten and rhenium as substrates and controls. After optimization of sputtering parameters such as sample bias, forward power, base pressure, and argon flow rates, coatings were obtained with a work function of 2.4–2.6 eV. At 1200 K, the emission density of a lanthanum hexaboride coated tungsten filament was 8.8 mA/cm2 while the emission density of a clean tungsten filament was 9.7×10−12 A/cm2. Coated tungsten filaments ran over 1000 h without any reduction in the emission current in a vacuum of 10−7 Torr. Coated filaments were flexed with moderate severity without microcracking, spalling, or a detectable difference in emission characteristics. After an initial activation, the lanthanum hexaboride-coated filaments were exposed to the atmosphere without a subsequent reduction in emission current density. Surface analysis indicated that the surface of the cathode was primarily lanthanum oxide.
Mechanisms of excimer laser cleaning of air-exposed Si(100) surfaces studied by Auger electron spectroscopy, electron energy-loss spectroscopy, reflection high-energy electron diffraction, and secondary-ion mass spectrometry
Authors: Tsu R. , Lubben D. , Bramblett T. R. , Greene J. E.
Published: July 2002

The structure and composition of air-exposed Si(100) surfaces irradiated by a KrF (248 nm, 5.0 eV, 22 ns pulses) excimer laser in ultrahigh vacuum (UHV) have been studied using Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), and reflection high-energy electron diffraction (RHEED). The near-surface region was compositionally profiled using secondary-ion mass spectrometry (SIMS). Pulsed laser irradiation at energies below the melting threshold (≊500 mJ cm−2 ) led to significant reductions in surface C and O concentrations but detectable contamination remained even after 200 pulses. However, surfaces exposed to several laser pulses at energies just above the melting threshold were atomically clean (less than 0.01 monolayer of impurities) as judged by AES and EELS and exhibited a 2×1 RHEED pattern. The peak in the EELS spectrum associated with surface dangling bond states was slightly lower in intensity and higher in energy than results obtained from thermally cleaned samples, while other surface states associated with the 2×1 reconstruction and noninteger RHEED streak intensities were also slightly less intense. SIMS profiles of the irradiated wafers revealed C and O impurities distributed throughout the melt volume. Thus, excimer laser irradiation produces clean Si(100) surfaces by a combination of desorption (accounting for approximately 1/3 to 1/2 of the decrease in impurity concentration) and dissolution leaving a disordered (2×1) surface. Annealing irradiated wafers at 600 °C for 1 min in UHV produced sharp 2×1 RHEED patterns and EELS spectra identical to those obtained from thermally cleaned (≥900 °C) surfaces.
Supported catalyst characterization
Authors: Wu X. , Bhatia S. , King T. S.
Published: July 2002

Small Ru- and Pt-containing mono- and bimetallic particles supported on silica were characterized using both theoretical thermodynamic simulations and experimental nuclear magnetic resonance (NMR) of chemisorbed hydrogen. The thermodynamic Monte Carlo simulations have provided detailed information on the morphologies, surface structures, and surface compositions of Ru–Cu and Pt–Cu bimetallic particles. For small Ru and Pt crystallites, a significant fraction of surface atoms populate defect-like edge and corner sites (e.g., 20% of total surface atoms for a particle with a dispersion of 0.31). These sites are preferentially occupied by copper. NMR of chemisorbed hydrogen is a surface-sensitive technique and has been used to measure the overall surface composition of the bimetallic particles and reveal subtle changes in the surface electronic environments due to addition of a second metal (copper) or a surface contaminant (chlorine or sulfur). The surface composition results determined from thermodynamic simulations are in agreement with those from proton NMR measurements for a series of 4% Ru–Cu/SiO2 and a series of 5% Pt–Cu/SiO2 bimetallic catalysts. Chlorine and sulfur are capable of inhibiting hydrogen chemisorption on Ru surfaces at a less-than-monolayer coverage. This observation and also the observed decrease in proton Knight shifts with increasing Cl coverage (less pronounced for S) on Ru surfaces were attributed to a short-ranged, ‘‘through-the-surface’’ electronic effect.
Secondary ion mass spectroscopic characterization of silver and aluminum diffusion in parylene
Authors: Dabral S. , Yang G.-R. , Lu T.-M. , McDonald J. F. , Bakhru H.
Published: July 2002

Aluminum and silver on parylene-n (PA-n) were explored as metallization options. The low resistivity of silver (1.6 μΩ cm) makes it suitable for interconnection applications. Al is a well studied and utilized metal. Al and Ag diffusion have been compared to that of Cu. The Al, Ag, and Cu were deposited by partially ionized beam (PIB) technique. PA-n, a low dielectric constant polymer, was vapor deposited. Diffusion of the metals was studied at anneal temperatures/time of 573–623 K/0.5 Hr using secondary ion mass spectrometry and Rutherford backscattering techniques. The metal diffusion in the PA-n was found to be very small. The Cu diffusion profiles were of low concentration but fairly deep. It was observed that the Ag diffused less than the Al, both in atomic concentration and diffusion depth. For these annealing temperatures and time, it was estimated that the diffusion coefficients for Al was about 0.4 × 10−13 cm2/s; for Ag was about 0.8 × 10−14 cm2/s at 573 K; and for Cu was about 0.6 × 10−13 cm2/s at 623 K. The diffusion coefficient of Cu in PA-n was found to be comparable to the diffusion coefficient in polyimides. A substantial reduction of diffusion due to higher ion acceleration (1–3 kV) during PIB metal deposition was observed. It was found that there was significant diffusion when Ag/Pa-n was annealed at 648 K.
Alloy formation energetics and dynamics in the Ni/Cu(100) and Ni/Cu(111) systems
Authors: Raeker Todd J. , DePristo Andrew E.
Published: July 2002

We investigate the diffusion, agglomeration, and alloy formation of Ni atoms and islands on Cu(100), Cu(111), and a stepped Cu(111) surface. Stochastic molecular dynamics simulations at constant temperatures are used in conjunction with the generation of all energies and forces from the semiempirical density functional based molecular-dynamics/Monte-Carlo corrected effective medium theory. At temperatures from 300 to 900 K, significant amounts of surface alloying occurs at step edges but not on terraces. The more favorable mechanism of alloy formation is for adatoms on the upper terrace to be incorporated near the step edge via displacement of the edge outwards. The alternative process of incorporation of an adatom on the lower terrace into the step is less favorable.
Radial dependence of silicon KVV and L23VV Auger matrix elements
Authors: Jennison D. R. , Weightman P.
Published: July 2002

We present calculations which show the radial dependence of the KVV and L23VV Auger matrix elements of silicon. We find greatly differing dependences, converging within ∼1 a.u. of the nucleus in the case of the KVV, but not until ∼4 a.u. in the case of the L23VV, well beyond the bond midpoint of ∼2.2 a.u. We also find quite different dependences for the various elements within a particular CVV transition. Because the local density of states (LDOS) is dependent on the radius of the sphere of integration, our results suggest that different CVV Auger processes on the same atom in fact probe different LDOSs, as do even different contributions within the same transition. (This effect is separate from the well-known matrix element property which weights angular-momentum components differently.) These results call into question both the single-site LDOS approximation when used in the interpretation of low-energy (<100 eV) Auger spectra, and the application to high-energy spectra of local densities of states obtained by integration over muffin-tin or Wigner–Seitz spheres which have a large radius compared to the region probed by the Auger process.
X-ray photoelectron spectroscopy characterization of a nonsuperconducting Y–Ba–Cu–O superconductor–normal-metal–superconductor barrier material
Authors: Vasquez R. P. , Hunt B. D. , Foote M. C. , Bajuk L. J.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) is used to characterize a new nonsuperconducting Y–Ba–Cu–O barrier material which has successfully been used in superconductor–normal-metal–superconductor (SNS) device structures, grown under conditions similar to those reported to yield a cubic phase (c-YBCO). Comparison of the XPS spectra to those obtained from the orthorhombic (o-YBCO) and tetragonal (t-YBCO) phases shows that the barrier material is distinct from either of the previously known phases. The O 1s spectrum from o-YBCO shows a main peak at 528.0 eV associated with Cu–O planes, a clearly defined shoulder at 527.1 eV associated with Cu–O chains, and a peak at 528.7 eV which variable angle measurements show is a surface peak, tentatively assigned to reconstruction of the surface-terminated Cu–O planes. The O 1s spectra from t-YBCO and the YBCO barrier material exhibit single peaks at 528.8 and 528.1 eV, respectively. The valence band of the barrier material is similar to that of o-YBCO, but narrower on the low binding energy side where the Cu 3d–O 2p π-bonding states from Cu–O chains occur. The lack of features corresponding to Cu–O chains or surface reconstructed Cu–O planes in the data from the YBCO barrier material is consistent with expectations from a previously proposed simple perovskite crystal structure for c-YBCO.
Synthesis and structure of a superconducting Au–Nb superlattice
Authors: Jankowski A. F.
Published: July 2002

A novel phase of Au0.5Nb0.5 is synthesized as a thin film using magnetron sputter deposition. A ‘‘multilayer’’ process is used to create an artificial superlattice by an atomic plane-by-plane alternation between Au and Nb. Resistivity measurements indicate the 0.32 μm thin film is superconducting at 2.5 K. Microstructure is determined using x-ray diffraction and transmission electron microscopy. The Au0.5Nb0.5 thin film has a body-centered-cubic structure which extends well beyond the limits of the reported, Nb terminal solid solution.
Effects of Ti–W target processing methods on defect generation during very large scale integrated device fabrication
Authors: Dunlop J. , Waterman E. , Brat T.
Published: July 2002

The relationship between Ti–W target manufacturing technique and deposited film quality is examined with an emphasis on film defect density. Three different target manufacturing methods are investigated; vacuum hot pressing (VHP), inert gas hot pressing, and hot isostatic pressing. The target composition in all cases is 18 wt % titanium, the configuration is seven inch diameter conical and two purity levels (99.95% and 99.995%) are evaluated. Target processing methods and microstructure results are discussed. Scanning electron microscopy micrographs show distinct differences in the amount of pure alpha titanium and the homogeneity of the titanium and tungsten rich beta Ti–W phases. The characteristics of films deposited from each of the three targets are investigated. Standard film properties are presented with an emphasis on film defect density as measured by several different methods. Transmission electron microscopy micrographs of the deposited film show distinct differences in film structure. Significant differences in defect density were also found with the VHP having the lowest overall defect density. A mechanism for defect generation due to pressure within target voids is discussed.
X-ray photoelectron spectroscopy study on InP treated by sulfur containing compounds
Authors: Kwok R. W. M. , Lau W. M.
Published: July 2002

Surface chemistry, and surface Fermi level (EFs) changes on InP, as a result of exposure to several sulfur compounds, and of subsequent heating were studied by x-ray photoelectron spectroscopy. It was found that after p-InP samples were exposed to a mixture of hydrogen sulfide and polysulfide, heating at 200–300 °C induced a strong type-inversion of the semiconductor surface. However, subsequent heating at 400 °C returned EFs towards the valence band maximum (VBM). From many repeated experiments, EFs was found to be changed in the range of 0.5–1.2 eV (referenced to VBM). Further studies on exposure to other sulfur compounds including hydrogen sulfide, sulfur, and sulfur dioxide showed that the large range of EFs movement correlated only with polysulfide. The overall spectral results suggest that adsorption of hydrogen polysulfide reduced surface states in the band gap of InP and led to the formation of donor states near the conduction band minimum of InP upon heating at 200–300 °C. Further heating at 400 °C desorbed the donor species and returned EFs towards the VBM.
Mechanical properties of thin films deposited by neutral beam assisted deposition
Authors: Gu P. F.
Published: July 2002

The adhesion and hardness of ZnS, MgF2, and cryolite films produced by neutral beam assisted deposition have been measured by using a simple scratch test and abrasion test. The results show that the mechanical properties are increased significantly when an energetic argon atom is used to assist in the deposition. Therefore, durable films are produced at low substrate temperatures.
Ion-driven permeation and surface recombination coefficient of deuterium for copper
Authors: Nagasaki Takanori , Yamada Reiji , Ohno Hideo
Published: July 2002

The flux density of deuterium permeation through polycrystalline copper membrane driven by an ion beam (5 keV D+3 ) was measured as a function of temperature (80–500 °C) and implantation flux [(0.2–1.0)×1015 D atoms cm−2 s−1 ]. The observed dependence of permeation flux on both parameters changed around 200–300 °C. This was found to be due to the transition in rate-controlling processes. The surface recombination coefficient of deuterium was evaluated from the permeation flux. In order to discuss it, the model for recombination coefficient based on one-dimensional potential-energy surface was extended, taking account of subsurface solution sites. The comparison between the experimentally and theoretically determined values supported the existence of the activation barrier for hydrogen chemisorption on copper.
Low energy metal ion source
Authors: Godechot Xavier , Brown Ian G.
Published: July 2002

We report here on some preliminary investigations of the characteristics of a metal vapor vacuum arc ion source operating in a low voltage mode so as to produce high current beams of metal ions at low energy. The 10-cm diameter, multiaperture beam formation electrodes were configured to an almost-symmetric accel–decel potential arrangement, and in this preliminary work the accel voltage was limited to just 4 kV. We produced a pulsed titanium ion beam with current up to 100 mA at 1.5 kV net extractor voltage.
Theoretical and experimental study of large aperture low energy e-beam source for semiconductor processing
Authors: Kovalev A. S. , Mankelevich Yu. A. , Muratov E. A. , Rakhimov A. T. , Suetin N. V.
Published: July 2002

Experimental and theoretical examination of the large aperture low energy electron beam source based on the design of a direct-current (dc) open discharge is made. This source has been tested as the etching system for both the monocrystal Si and the photoresist under the different gas mixtures. This dc system appears to be used to treat insulators. The numerical model to simulate plasma processes in the considered system is developed. Results of model simulation are compared with the experimental data.
Aluminum–4% Cu interconnect etching in a low-pressure magnetically enhanced reactor
Authors: Narasimhan M. , Sasserath J. , Ghanbari E.
Published: July 2002

A novel approach has been used to obtain residue-free dry etching of Al–4% Cu alloy interconnects with chlorine-based plasmas. The addition of external aluminum in a magnetically enhanced plasma etch reactor was used to form AlCuClx, a volatile etch by-product. Response surface methodology was used to explore the parameter space for a hydrocarbon-free BCl3/Cl2-based chemistry. Total gas flows between 60 and 80 sccm, rf power levels between 800 and 1000 W, and BCl3/Cl2 ratios of 0.1–0.25 were found to lead to optimal etches. The response variables studied were Al etch rate, photoresist etch rate, SiO2 selectivity, and post-etch residue. Al etch rates of 4500 Å/min, photoresist selectivities of 1.5:1, and SiO2 selectivities better than 5:1 were obtained. Optical emission spectroscopy was used to monitor the removal of the Cu-rich residue by observing emission intensities of the 325-nm Cu line.
Impurity and recycling control with gettering in the Advanced Toroidal Facility
Authors: Simpkins J. E. , Mioduszewski P. K. , Isler R. C.
Published: July 2002

The vacuum vessel of the Advanced Toroidal Facility (ATF) is Ti gettered with a surface coverage of 70%. The major effects of gettering are (1) reduction of the oxygen, carbon, and nitrogen content in the plasma and (2) improved density control due to wall pumping of the working gas hydrogen. The overall leak rate in ATF is 2×10−4 Torr ℓ/s which is too high for successful plasma operation. Ti gettering is routinely employed every morning prior to operation and compensates for this shortcoming by reducing the partial pressure of nitrogen and other residual gas components to the low 10−9 Torr range which is close to the residual gas analyzer background pressure. Rate-of-rise measurements at this stage show only argon and some methane. The argon is used to monitor the leak rate. In addition to impurity reduction, gettering leads to low recycling of the working gas which appears to be crucial for density control in ATF. The capacity of the gettered surface is large enough to show a strong effect even after 24 h. An extensive data base on the short-term and long-term effects of gettering on the residual gas composition and its effects on plasma performance has been established over the past three years and will be discussed in this article.
Plasma–materials interaction issues for the International Thermonuclear Experimental Reactor (ITER)
Authors: Cohen S. A. , Mattas R. F. , Werley K. A.
Published: July 2002

At the extreme conditions expected for some operating scenarios of the International Thermonuclear Experimental Reactor, commonly used heat-removal structures are unable to withstand either the high sputter erosion rates or power loads. Solutions to these lifetime and reliability problems by (1) changes in machine design and operation, (2) redeposition mechanisms, and (3) changes in materials, will be discussed. A proposed accelerated-life test facility for prototype divertor plate development is described.
Numerical model of bombarding ions energy distribution function in magnetron discharge
Authors: Lukyanova A. V. , Rakhimov A. T. , Suetin N. V.
Published: July 2002

We present a self-consistent numerical model of magnetron radio-frequency discharge using the hydrodynamic approximation. The model allows one to simulate the energy distribution function for ion beams on the discharge boundary. The simulation results are in qualitative agreement with the experimental data. Besides, some analytical formulas for the ion energy distribution function parameters are derived and compared with numerical calculations.
Effects of initial growth conditions on the stress profiles of Mo sputtered onto both moving and stationary substrates
Authors: Bell Brent C. , Glocker David A.
Published: July 2002

In order to understand the influence of the initial growth conditions on stresses in films deposited on scanning substrates, we have made in situ measurements of the stress profiles of Mo sputtered onto stationary and moving glass beams under a variety of conditions. Stationary coatings made directly above the center of the target had stresses ranging from −1.33 GPa at 2.5 mTorr to +1.81 GPa at 10 mTorr. At 2.5 and 5.0 mTorr, films deposited on substrates at rest near the edge of the coating zone were considerably more tensile than films grown directly above the target, while films on scanned substrates were only slightly more tensile than those deposited above the target. At 10 and 15 mTorr, films grown under all three conditions had almost the same high level of tensile stress. Coatings were also made directly above the target at 2.5 mTorr onto tensile films with thicknesses which were varied. A 24 nm thick underlayer had little effect on the stress of the subsequent coating, but deposition on top of a 135 nm thick tensile film produced a stress profile which initially followed that of the underlayer, became compressive, and reached a value of −0.64 GPa after 100 nm of additional growth. We conclude that sufficiently thick high-angle initial growth can affect the stress profile of subsequently deposited material. However, in web or palletized coatings where only a small amount of material is deposited at high angles, the influence is small.
Synthesis and structural characteristics of ion-beam sputtered multilayer Ag/Al thin films
Authors: Kim C. , Qadri S. B.
Published: July 2002

Multilayers of Ag/Al with layer thickness ratio of 1.7:1.0 have been deposited on Si and glass substrates using ion-beam sputtering with composition modulation wavelengths λ ranging from 13.5 to 213 Å. Spatial distribution and angular dependence of deposition rates were determined by analysis of x-ray diffraction scans which showed several orders of distinct satellite peaks and well defined small angle peaks. At high modulation wavelengths (λ≳35 Å), the multilayer film showed (111) preferred orientation normal to film plane. For short modulation wavelengths (λ<35 Å), other orientations appeared and peaks corresponding to Ag2Al intermetallic phase were also observed. One satellite peak corresponding to Ag2Al(100) peak was observed and gave the same modulation wavelength as the parent Ag/Al multilayer. The computer simulation analysis using square wave model is in good agreement with the observed satellite peak positions for high modulation wavelengths. The average lattice parameter of the Ag/Al multilayer reduces by 1.1% as the modulation wavelengths drops below 35 Å, which may be partially attributed to the presence of a significant proportion of Ag2Al interphase layers at the interface.
Influence of surface contaminants on W film growth on Si(100) from WF6
Authors: Lantz S. L. , Ford W. K. , Bell A. E. , Danielson D.
Published: July 2002

The influence of residual O and C contaminants on the adsorption of WF6 on Si(100) was characterized using Auger electron spectroscopy and secondary electron microscopy. Samples cleaned using an ultrahigh vacuum sputter-etch process were free of contaminants. Upon WF6 exposure, a smooth W film developed that was homogeneous on a 100 nm length scale at deposition temperatures from 300 to 550 °C. An effective activation energy for the WF6+Si reaction was measured to be 0.16±0.03 eV. Chemical and x-ray diffraction analysis showed silicide formation at temperatures above 450 °C. Si(100) samples cleaned using a wet HF dip exhibited residual O and C contamination. WF6 exposures to these surfaces led to discontinuous films with large pores, ∼300 nm, for deposition temperatures above 450 °C. The effective activation energy increased to 0.26±0.05 eV. The chemical reaction on the contaminated surface exhibited a temperature dependent induction period of the order of 50 L, in which little W is deposited. The induction period is associated with the formation of a porous W–O layer.
Observation of nanometer ordering in multilayer films of pyromellitic dianhydride–oxydianiline using the scanning tunneling microscope and ultrahigh vacuum
Authors: Schulman Erica N. , White R. C.
Published: July 2002

We have obtained topographic images and spatially resolved spectroscopic information of uncoated pyromellitic dianhydride–oxydianiline (PMDA-ODA) films. We find that prolonged exposure to vacuum is a key to successful imaging of this nominally insulating film surface. It is postulated that water desorption from the film is responsible. This mechanism may apply to many other organic materials. Topographic results indicate that there is a fair amount of ordering in this polymer, at least for dip-coated films. Finally, we see that PMDA-ODA has low-density states very close to the pseudo-Fermi energy, in contrast to the wide band gap predicted by ultraviolet photoelectron spectroscopy results. This provides an explanation for the anomalous conductivity seen in these thin films.
Interaction of molecular BF+ and BF+2 ions with gold surfaces at low energies: Neutralization, dissociation, and deposition
Authors: Shen Y. G. , Huang L. J. , Lau W. M.
Published: July 2002

The surface reactions induced by BF+ and BF+2 bombardment of gold at 10–250 eV were studied with a mass-separated low energy ion beam system. The energy distributions of dissociative ion fragments and survival molecular ions were measured by low energy ion scattering with a scattering angle of 90° and polar incident angle of 45°. The results suggest that neutralization of BF+ and BF+2 via resonance charge transfer, Auger neutralization, and collisional charge exchange all contribute to the reduction of the parent ion intensity. In the study of dissociative scattering, the observed onset values of 35 eV for BF+ dissociation and 20 eV for BF+2 dissociation indicate that dissociation occurs mainly via vibrational excitation at impulsive collision with the surface. In addition, secondary ion mass spectrometry, secondary neutral mass spectrometry, and x-ray photoelectron spectroscopy analyses of gold surfaces bombarded with BF+ and BF+2 show that the dissociation also leads to the accumulation of boron and boron fluorides on gold.
Site requirements of reactions on oxide surfaces
Authors: Barteau Mark A.
Published: July 2002

The development of structure-reactivity relationships has been a long-standing goal of surface science studies. Ironically, though they have been considered much less often than metals, metal oxides appear to offer some of the best opportunities for developing such relationships. The localized electronic structure of oxides permits connections to be drawn from reactivity to the discrete coordination environments and oxidation states of surface cations, and thence to coordination chemistry of metal complexes in solution. Reactions of carboxylic acids on different oxide single crystal surfaces illustrate the roles of surface coordinative unsaturation, oxidation state, and redox properties in determining the surface reactivity of metal oxides.
On the nature of zero temperature coefficient of resistance of RuO2 thin film resistor formation using in situ annealing
Authors: Jia Q. X. , Jiao K. L. , Anderson W. A. , Collins F. M.
Published: July 2002

Thin film RuO2 resistors with a temperature coefficient of resistance (TCR) around 0±20 ppm/°C were reproducibly deposited on ceramic alumina substrates using reactive direct-current (dc) magnetron sputtering at room temperature followed in situ annealing of the film at 250 °C in oxygen for 60 min. The electrical resistance of the films was monitored in real time and temperature during the in situ annealing. The TCR of the films was irreversible during increasing and decreasing temperature. Auger electron spectroscopy depth profiling on the film with a near zero TCR fabricated in such a way revealed layerlike structure of the resistors. The top region of the film was near stoichiometric, whereas the bottom region was oxygen deficient.
Auger analysis of chromium films evaporated on polyimide
Authors: Jinkins Jane G. , Davis Robert E.
Published: July 2002

The use of evaporated chromium as an intermediate layer to provide adhesion between polyimide (PI) insulator materials and other metals has numerous applications throughout first-level microelectronics packaging. In this work, PI substrates are considered to determine microprocess environments during electron beam evaporated deposition of Cr, with possible ramifications for the integrity of the Cr/PI interfaces. Auger electron spectroscopy (AES) analysis-in-depth was used to evaluate electron beam evaporated chromium thin films (1000 Å) both as-deposited and after a simulated assembly process in which the Cr/PI structures were heated to 150 °C. The AES results indicated that the effects of water outgassing from the PI substrate during deposition were the dominant influence on oxidation of chromium as opposed to subsequent thermal processing. It was found that the degree of water outgassing, and thus the extent of incorporation of O into growing Cr films, was determined by both the cumulative thickness of the PI underlayers and the thermal processing of these PI structures prior to deposition, all other things remaining the same. The greatest amount of oxygen [∼20% Atomic Concentration (AC)] incorporated throughout the layer of Cr was for a substrate which contained multiple levels of PI having a total thickness of 21 μm which was patterned with interconnecting metallurgy. A ∼4X decrease in both the number of wiring levels and total PI thickness resulted in a reduction of oxygen in the bulk Cr to just detectable levels. The final cure temperature of the PI for these structures was 350 °C. An increase in the final cure temperature to 400 °C prior to deposition of Cr was also found to reduce the amount of O; for the same thickness of PI, the level of oxygen in the Cr decreased from 20% to ∼15% AC. The effects of a postdeposition thermal anneal in nitrogen ambient on Cr oxidation was assessed for all types of structures; there was no measurable increase in chromium oxidation found for any of the samples after they were annealed at 150 °C.
Measurements of neutral species in low pressure C2F6 discharges using diode laser absorption spectroscopy
Authors: Sun H. C. , Patel V. , Whittaker E. A. , Singh B. , Thomas J. H.
Published: July 2002

We report the first diode laser spectroscopic investigation of low pressure C2F6 discharges which are commonly used for plasma etching of silicon dioxide. A new high sensitivity technique that utilizes combined wavelength and frequency modulation technique has been developed that permits individual species in gas discharges at very low pressures to be monitored. In situ measurements of the relative concentrations of the oxide etchant radicals such as CF3 and CF2 in a pure C2F6 plasma were performed in a production compatible, multiconfiguration, parallel-plate plasma etching reactor. Comparative data for the reactor configured as a diode, a triode, and a magnetic multipole enhanced triode are presented. The total pressure was varied from 0.62 to 87 mTorr. Data obtained show that both the reactor geometry and the total gas pressure have significant effects on the overall species population. The results also show that the magnetic multipole enhanced triode has a much higher efficiency for generating the etchant radicals at lower pressure than the other geometries.
Effects of aluminum sputtering target surface grain relief and crystallographic orientation on sputtering I–V characteristics
Authors: Leybovich A. , Kuniya T.
Published: July 2002

The effects of Al sputtering target surface grain relief and crystallographic orientation on magnetron sputtering target I–V characteristics have been investigated to reveal the nature of I–V characteristic deviations. Eight aluminum single crystals, three polycrystalline Al-1 wt % Si targets with different degrees of (100), (110), and (111) crystallographic orientations and three polycrystalline Al-1 wt % Cu targets with grain sizes of 0.25, 0.95, and 5.5 mm were used. Square grid patterns were machined into the sputtering surface of five of the (110) and one of the (111) single crystals to simulate the surface grain relief and the (110) or (111) preferred crystallographic orientations of polycrystalline targets. These patterns consisted of intersecting grooves with dimensions comparable to target grain sizes and plasma sheath thicknesses. Groove depth to width aspect ratios ranging from 0.067 (20/3000 μm) to 0.33 (100/300 μm) were used. I–V measurements with patterned and nonpatterned single crystals showed that both crystallographic orientation and surface relief affect the I–V characteristics. (110) single crystal targets decreased the target bias voltage when compared with (111) single crystal targets. A minimum in target voltage was found at intermediate values of aspect ratio. For polycrystalline Al-1 wt % Si and Al-1 wt % Cu targets minimum target voltage was obtained using targets with the smallest degree of (111) crystallographic orientation and 0.95 mm grain size.
Saddle-field ion source deposition of conductive thin films
Authors: Cardinale G. F. , Howitt D. G.
Published: July 2002

Thin films of iridium and gold were deposited using the saddle-field source with argon as the sputtering gas. The purpose of this investigation was to determine the effects of deposition parameters on the grain size and composition of the films with thicknesses of 1.0, 2.5, and 5.0 nm, which are typical of the coatings used for high resolution electron microscopy. The films were deposited onto amorphous carbon films using ion beam sputtering, and as expected, the grain size of the films increased with the thickness, and the average grain size showed a dependence on the ion source energy. No oxides were formed in either the iridium or gold films.
Instability of the metal microcrystal surface at intense electron emission*
Authors: Ptitsin V. E.
Published: July 2002

Some elementary processes are examined, that cause instability of thermal field emission (TFE) current from the thermal field cathode (TFC) tip surface in a strong electric field (Fs≳0.45B/Å). Thermal calculations of TFC apex heating by TFE current have yielded a simple analytical expression for the TFE current limiting density. It is shown that at high TFE current densities (close in the order of magnitude to the limiting value), the TFE current instability is connected with the instability of the TFC emitting surface. The time needed for the field ionization of the desorbing (W) atoms is calculated.
Spin correlation effects on the bonding character of alkali/silicon interfaces: An extended Hubbard model
Authors: López-Sancho J. M. , Refolio M. C. , López-Sancho M. P. , Rubio J.
Published: July 2002

Recent calculations strongly suggest assuming an antiferromagnetic spin arrangement for the Si(100)-(2×1) reconstructed surface. The implications of this assumption for the alkali-covered surface are here studied by means of an extended Hubbard model. Whereas the substrate undergoes a gradual insulator-to-conductor transition with increasing coverage, the adlayer suddenly metallizes above a critical coverage value. Recent core-level data are not incompatible, as previously believed, with an ionic bond description of this interface.
Accurate determination of delay time and length of flight path for a time-of-flight modulated molecular beam apparatus
Authors: Wu P. K. , Hudson J. B.
Published: July 2002

Curve fitting procedures for time-of-flight distributions arising from modulated molecular beams have been examined using synthesized data. It was found that the signal-to-noise ratio in the data and the number of fitting variables used in the fitting procedure strongly influence the accuracy of the fitting result. A procedure for accurate determination of the delay time and length of flight path for at time-of-flight machine is established. With this new procedure, the number of fitting variables can be reduced from 5 to 3, both improving the accuracy of the result and reducing processing time. The procedure performs well when applied to either synthesized data or experimental results.
Structural change of titanium oxide evaporated films during in situ heating in an electron microscope
Authors: Yamada Y. , Shiota I. , Yoshida K.
Published: July 2002

Structural changes of titanium oxide films, formed by evaporating TiO1.0 on NaCl substrates held at various temperatures, have been studied during in situ heating in an electron microscope. It has been revealed that the evaporant decomposes partially into titanium and oxygen ions during the evaporation. As-deposited films composed of both hexagonal-close-packed (hcp) and NaCl-type crystallites are oxidized by heating at about 600 °C and the crystal structures of the film transform finally into the transition structure I in which titanium vacancies are ordered. On the way toward the transformation, crystals of the transition structure II in which oxygen vacancies are ordered, grow and the δ-phase single crystals (ad=4.982 Å, cd=2.894 Å) precipitate also. On the basis of the examination of the structural relationship between the δ-phase and the hcp α-phase crystals, the former crystals are considered to be grown from the latter crystallites. The distortion of the transition structure I and II from the parent NaCl-type lattice is also discussed.
Nuclear polarization of solid deuterium–tritium
Authors: Souers P. C. , Tsugawa R. T. , Fearon E. M. , Collins G. W. , Maienschein J. L. , Failor R. A. , Mapoles E. R. , Fedders P. A.
Published: July 2002

We have investigated both theoretically and experimentally the properties of condensed D–T as they apply to nuclear polarization for hydrogen fusion. At 2 K, atom densities and their electron relaxation times were found to be sufficient to pump nuclei in the process of dynamic nuclear polarization. However, the nuclear spin lattice relaxation times of both the triton and deuteron were too short by 2–3 orders of magnitude, as a result of the creation of rotationally excited hydrogen (J=1 T2 and D2) by the tritium radioactivity. Three means of lengthening these times are discussed: (1) synthesizing low J=1 molecular DT (here, J is the molecular rotational quantum number), (2) synthesizing high J=1 D2–T2 in the ordered phase, and (3) placing the sub-2 K solid in fine-celled foam. The most likely method combines the first and third approaches. Even so, the purified solid DT is likely to last only 20–30 min before the tritium radioactivity reduces the relaxation times. The best temperature regime is in the low-temperature solid; the conditions of the solid at 14–18 K and the liquid at 21–23 K are not considered favorable for nuclear polarization. The first synthesis of pure DT using an adsorption column at 23 K is demonstrated.
Poor man’s scratch tester
Authors: MacGill R. A. , Yao X. Y. , Castro R. A. , Dickinson M. R. , Brown I. G.
Published: July 2002

We describe a simple scratch tester for use in the evaluation of the scratch/adhesion characteristics of material surfaces. Its simple design makes it very inexpensive and easy to assemble and operate. We have used the device for investigating improvements in the hardness of ion implanted copper and in the adhesion of alumina films ion stitched onto a steel substrate.
Simple, compact, high-purity Cr evaporator for ultrahigh vacuum
Authors: McClelland J. J. , Unguris J. , Scholten R. E. , Pierce D. T.
Published: July 2002

A simple, compact Cr evaporator is constructed by electroplating Cr metal onto the tip of a W hairpin filament. At 5 cm from the evaporator, deposition rates up to 10 nm min−1 (flux ≊1019 atoms m−2 s−1) have been obtained, with total deposition thickness in excess of 400 nm. Auger analyses of thin films deposited in ultrahigh vacuum show impurities below detectability.
Design and performance of a novel powder flash evaporator
Authors: Shepherd J. A. , Sobottka S. E. , Williams M. B.
Published: July 2002

We have designed a high vacuum powder flash evaporator source with potential for ultrahigh vacuum applications. The powder is transported to the resistance-heated boat inside a sloping, vibrating, tube. The evaporator is novel in that the transport tube is driven by a piezoelectric motor connected to a low-power frequency generator. When loaded with powder ground from single crystals of NaI(Tl), the evaporator has been successfully used to create 25-μm-thick films of NaI(Tl) having homogeneous thallium concentrations. The powder feeder is inexpensive in comparison to other vapor sources (sputter, e beam, wire feed, etc.) typically used to deposit alloys and impure materials. This paper discusses the design and application of the flash evaporator.
Ir–Zr alloys as diffusion barriers between Cu and Si(100)
Authors: Yang H. , Gilmore C. M. , Ramaker D. E.
Published: July 2002

Various Ir–Zr alloys were studied to determine their effectiveness in high temperature applications as diffusion barriers at a Cu/Si interface. Samples were characterized with x-ray diffraction, Auger electron spectroscopy, Rutherford backscattering spectroscopy, and resistivity measurements. An amorphous Ir0.84Zr alloy was found to be a more effective diffusion barrier than a polycrystalline Ir2.85Zr alloy, indicating that grain boundary diffusion dominates in the Ir2.85Zr film. The films, typically about 3000 Å thick, were found to serve as effective diffusion barriers for temperatures up to about 800 °C. The diffusion constants were determined at various temperatures, and the activation energy for Si out-diffusion in Cu/Ir0.84Zr/Si was also obtained.
New flow behavior of gases and vapors in vacuum at very low flow rates
Authors: Venkataramani N. , Ghezzi F. , Bonizzoni G.
Published: July 2002

An investigation of flow of gases and vapors in vacuum through a path of very small cross-sectional area, namely that of a high vacuum gas leak valve, reveals the existence of a new flow behavior which is well behaved. The characteristics are different from that of the molecular flow or that of the sonic flow through a small aperture. The unambiguous nature of the flow has been observed by three independent flow measurement techniques. The conductance is found to decrease with the pressure upstream and depends on the geometry and specie. The effect of the residence time of the gas molecules during the collisions with the wall of the conducting path has been attributed as a possible mechanism to explain the observed flow phenomenon. The flow behavior has also been studied for two isotopic water vapors. Based on the defined characteristics of the flow, an application technique is proposed for finding the partial pressures of the component vapor and gases in a low-vacuum system by making the measurements in a coupled high vacuum system using a quadrupole mass analyzer. The applicability and sensitivity of the technique are demonstrated by an example measurement of the compositions of hydrogen and oxygen gas mixture.
Effect of a magnetic field on the deposition of TiO2 films
Authors: Albertinetti N. , Minden H. T.
Published: July 2002

In the process of making magnetic mirrors for ring laser gyroscopes a hard multilayer dielectric stack was deposited in the presence of a magnetic field. The thickness of the TiO2 layers was nonuniform while the thickness of the SiO2 layers was unaffected by the magnetic field. The thickness distribution was determined and the thickness variation of a single layer was measured. Speculations are presented as to the origin of the effect.
Deposition of silicon oxide films from TEOS by low frequency plasma chemical vapor deposition
Authors: Tochitani G. , Shimozuma M. , Tagashira H.
Published: July 2002

Recently, TEOS has been studied as a silicon source of silicon oxide films deposited by plasma chemical vapor deposition (CVD) because the deposited films show good step coverage compared with films deposited from SiH4. In this work, the authors deposited silicon oxide films using TEOS as a silicon source by using a low frequency (50 Hz) plasma CVD. It has been demonstrated in previous articles that low frequency (50 Hz) plasma CVD can deposit high quality silicon nitride films and amorphous carbon films without substrate heating. It is found in the present work that the substrate heating at deposition is required to obtain acceptable electrical properties when silicon oxide films are deposited from a TEOS and oxygen mixture, even by low frequency (50 Hz) plasma CVD. The films deposited at 200 °C from the plasma of a 3% TEOS mixture were found to be high quality insulating films; the resistivity was 1016 Ω cm and the breakdown strength 7×106 V/cm. Moreover, Auger electron spectrum analysis revealed that carbon atoms were not detected from the films in spite of the presence of carbon atoms in the TEOS molecule. With optical emission spectrum analysis of the TEOS and oxygen mixture plasma, strong emissions from the CO and CO2 molecules were observed. It may be concluded that in the plasma carbon atoms react with oxygen atoms to yield the CO and CO2 molecules which are stable enough to remain in the gas and thus not be taken into the films.
On the optical properties of an electrostatic retarding field lens
Authors: Wang Y. L. , Lai M. Y. , Shao Zhifeng
Published: July 2002

The optical properties of an electrostatic retarding field lens, which consists of an einzel lens and a retarding field between its exit and the image plane, are analyzed using both analytical and numerical methods. The results show that such a compound lens can be well approximated by a combination of three optical components: the einzel lens, an aperture lens superimposed at its exit, and a uniform field between its exit and the image plane. When the distance between the exit and the image plane is long, and a strong retardation is required for forming a low energy beam, the performance of such a compound lens is dominated by the chromatic aberration of the retarding field. Using this lens and a liquid metal ion source, it is possible to form a low energy (100 eV) focused ion beam with a diameter and current density of 1000 Å and 1 A/cm2, respectively.