bluuebunny/crossref_metadata_2025 huggingface dataset:
Imaging of laser generated surface ripples on silicon
Authors: Heil J. , Wesner J. , Hillmann K. , Grill W. , Altschoeller K. , Niksch M.
Published: July 2002

A scanning tunneling microscope is presented which is able to supply image data from the micrometer range down to atomic scales. By laser annealing corrugations can be generated on semiconductor surfaces with periodicities close to 1 μm. A bimorph scanner has been used to obtain large-scale topographic maps of these structures.
A synchrotron radiation study of BaO films on W(001) and their interaction with H2O, CO2, and O2
Authors: Mueller Donald , Shih Arnold , Roman Elisa , Madey Theodore , Kurtz Richard , Stockbauer Roger
Published: July 2002

The interaction of O2, CO2, and H2O with bulk BaO and BaO adlayers adsorbed on W(001) has been examined using ultraviolet photoelectron spectroscopy. H2O reacts with bulk BaO to form Ba(OH)2, while CO2 forms a surface layer of BaCO3. Water and carbon dioxide also react with a (√2×2)R45–BaO monolayer adsorbed on W(001) to produce adsorbed OH and CO3 species bound to the tungsten substrate. The interaction of O2 with W(001) is enhanced by the presence of a BaO monolayer on the substrate. The observations are compared with the results of previous studies.
Hydrogen isotope trapping on graphite collectors during an isotope exchange experiment in the Tokamak Fusion Test Reactor
Authors: Kilpatrick S. J. , Nygren R. , Wampler W. R. , Ulrickson M. , Dylla H. F. , Manos D. M. , Ramsey A. T. , Hirooka Y.
Published: July 2002

A rotatable collector probe was used to expose several graphite samples to a deuterium-to-hydrogen-to-deuterium exchange experiment in the Tokamak Fusion Test Reactor (TFTR) at the start of the 1988 operations period. This experiment proved the utility of helium conditioning discharges in accelerating the changeover process. Samples included portions of a tile taken from the inner bumper limiter (POCO AXF-5Q graphite) of TFTR during the recent machine opening, and coupons which had been conditioned in the Plasma Interactive Surface Component Experimental Station (PISCES) by exposure to a helium plasma. The samples were exposed to different groups of the ∼100 1.4 MA discharges that comprised the experiment. They were removed and analyzed for retained deuterium and impurities by nuclear reaction analysis and Rutherford backscattering spectrometry. Codeposited carbon layers had been formed with thicknesses up to several tenths of a micron. The inferred percentages of trapped hydrogenic species were in general agreement with spectroscopic data. The computed carbon fluence per D+ discharge, 1.2×1017 C/cm2, is compared to recent measurements on limiter tiles removed from TFTR.
The interaction of water with Pd(110)
Authors: Brosseau R. , Ellis T. H. , Morin M.
Published: July 2002

The properties of water layers adsorbed onto Pd(110) at 100 K have been studied with high-resolution electron energy-loss spectroscopy (HREELS) and temperature programmed desorption (TPD). A chemisorbed layer is observed which desorbs at 193 K. HREELS measurements suggest that this layer grows in two stages. At low coverage, the spectra are consistent with monomers or dimers. At slightly higher coverage, the spectra are consistent with the ‘‘bilayer’’ structure which has previously been proposed for Ni(110) and Cu(110).
Digital chemical vapor deposition and etching technologies for semiconductor processing
Authors: Horiike Y. , Tanaka T. , Nakano M. , Iseda S. , Sakaue H. , Nagata A. , Shindo H. , Miyazaki S. , Hirose M.
Published: July 2002

A novel concept on digital chemical vapor deposition (CVD) and etching technologies is described. ArF excimer laser irradiation to a condensed Si2H6 layer on a substrate cooled to −70 °C has resulted in spatially selective poly-Si film growth. The adsorbate thickness control by gas pressure and substrate temperature allows shot by shot atomic layer growth of Si. Digital CVD of SiO2 is also achieved by a repetitive cycles of silane radical deposition and subsequent oxidation. This reaction is promoted by an alternate introduction of pulsed microwave-discharged SiH4 and O2 beams. The deposition species ejected with supersonic velocity into the high vacuum reactor fills SiO2 into a deep trench. Also, digital etching of Si monolayers has been studied for the goal of damage-free etching. A preliminary result obtained by repeating the reaction cycle consisting of adsorption of fluorine atoms on a Si surface cooled to −100 °C and subsequent Ar+ ion irradiation has realized atomic layer etching of Si(100).
Measurement and analysis of radio frequency glow discharge electrical impedance and network power loss
Authors: Butterbaugh J. W. , Baston L. D. , Sawin H. H.
Published: July 2002

Impedance measurement of rf glow discharges is a convenient diagnostic tool that can be used to estimate specific discharge properties based on a simple electrical analog model. Accurate measurements require minimization and characterization of stray impedance. In this study, the stray impedance is minimized by using a triaxial power feedthrough and electrode shield configuration. The remaining stray impedance is characterized using a two-port circuit model to represent the impedance between the voltage and current probes and the electrode. The two-port parameters are determined by unterminating [R. F. Bauer and P. Penfield, Jr., IEEE Transactions on Microwave Theory and Techniques MTT-22, 282 (1974)] the network, which involves measuring the impedance of the reactor system with three or more known impedances inserted between the electrodes. Based on voltage and current measurement, the discharge impedance can then be determined during discharge operation. Impedance measurements and property estimations are made for Ar, CF4, and SF6 discharges. The actual power dissipated in the discharge is found to be as low as 10% of the power into the matching network for some Ar and CF4 discharges.
Impact of vacuum equipment contamination on semiconductor yield
Authors: O’Hanlon John F. , Parks Harold G.
Published: July 2002

Contamination control in semiconductor device manufacturing has always been considered an important topic by those working in the field. However, its importance by others has not been uniformly recognized. In this paper we bring a different perspective to the issue by beginning with a discussion of the economics of chip manufacturing. An example chip is chosen, and the effect of the efficiency of various sectors on the overall plant profit are considered. It is shown for this model, that in a well functioning fab, a 1% decrease in yield will cause ≳2% decrease in profit, for a sales price of 2× the manufacturing cost. Specific examples of contamination in vacuum-based equipment for semiconductor processing are used to illustrate that contamination, often attributed to handling and other factors, may be due in whole or in part by the equipment and/or the process. These examples make clear the economic impact of contamination on the automation, reliability, and design of equipment and processes.
Optical emission spectroscopy of zinc sulfide etch
Authors: Orloff Glennis J.
Published: July 2002

Optical emission spectroscopy was used to gain insight into the reactive ion etching (RIE) of zinc sulfide films in a hydrogen plasma. Evaporated, metal organic chemical vapor deposited (MOCVD), and sputtered zinc sulfide films were examined. The zinc atomic emission at 472 nm was used to monitor the etching reaction. Hydrogen atom emissions at 656 and 486 nm were also explored but were found to be less sensitive to the etching reaction. The zinc atomic emission data was found to be a very reproducible method of end point detection and was sensitive to etch rate, uniformity, and mechanism differences among the evaporated, MOCVD, and sputtered ZnS films. End point detection was demonstrated for patterned and unpatterned samples. Implementing end point detection for this reaction eliminates the problems associated with overetching and the need for separate processing parameters for each type of ZnS film.
Adsorption of hydrogen on Fe(110) at cryogenic temperatures investigated by low energy electron diffraction
Authors: Nichtl-Pecher W. , Gossmann J. , Hammer L. , Heinz K. , Müller K.
Published: July 2002

A cryosample holder was constructed and used to investigate the adsorption system H/Fe(110) at temperatures down to 35 K. We find a new 2×2-2H superstructure with a graphitic arrangement of adatoms which reversibly transforms to the well-known c(2×2) phase at a critical temperature of about 80 K. We give arguments that in both phases hydrogen induces the same type of a weak substrate reconstruction. Also, we propose a structural model according to which the c(2×2) phase is equivalent to the 2×2 phase, however, with additional local disorder imposed by thermally fluctuating occupation of neighboring threefold coordinated sites by the adatoms.
Postionization of sputtered neutrals by a focused electron beam
Authors: Gersch H.-U. , Wittmaack K.
Published: July 2002

We have explored a novel approach of electron-impact postionization involving the use of a focused low-energy electron beam directed at the flux of sputtered particles in very close proximity to the sample surface [‘‘matched’’ e-beam sputtered neutral mass spectrometry (SNMS)]. The first version of an electron gun developed for this purpose delivers a 300 eV beam of ∼100 μA into a 100 μm spot. The postionization efficiency was investigated in a quadrupole based ion microprobe using samples of germanium and gallium arsenide bombarded with 10 keV Ar+. Singly and multiply charged species Mn+ (with n up to 5 for As) were produced by electron impact. The position and size of the electron beam with respect to the ion beam could be controlled and optimized by recording raster scanning ion images of the postionized species. Inspection of the energy spectra showed that the ionization probability is larger the lower the velocity of the sputtered neutrals. At low energies (<5 eV) and with the maximum electron current density presently achievable, the intensity ratio of singly charged postionized atoms to secondary ions was ≊1 for Ge and ≊5 for As. Fractional ion yields of 2×10−8 and 3×10−8, respectively, are estimated for these species. These numbers are higher by more than one order of magnitude than the yields obtained previously by ‘‘remote’’ e-beam SNMS. Interference with the secondary ion flux was small or negligible in the case of doubly and multiply charged ions. The fractional ion yields for doubly charged ions ranged from 3 to 5×10−9. The results are compared with available cross sections for electron impact ionization. The measured SNMS ion yields are briefly compared with yields that can be achieved by charge transfer ionization using Ar+ beams at maximum current density. Advantages and limitations of the matched e-beam SNMS technique are discussed together with conceivable improvements using a more advanced electron gun and an improved ionization and ion extraction geometry.
Characterization of the B/Si surface electronic structures
Authors: Cao R. , Yang X. , Pianetta P.
Published: July 2002

High-resolution angle-resolved core-level and valence-band photoelectron spectroscopy have been used to characterize the electronic structures of the B/Si (111)-(√3×√3) surfaces. The results have been compared with theoretic calculations and other group-III metals and Si-terminated Si (111) surfaces that share the same type of surface reconstruction. We have observed a structure evolution from B-T4 to B-S5 and finally to Si-T4 as deposited boron atoms diffuse into the substrate with increasing annealing temperature. The chemically shifted component appearing in the Si 2p core-level spectrum is attributed to charge transfer from the top layer Si and Si adatoms to the sublayer B-S5 atoms. For the Si/Si (111)-(√3×√3) surface, a newly discovered chemically shifted component is associated with back bond formation between the Si adatoms and the underneath Si atoms. A new emission feature has been observed in the valence-band spectra unique to the B/Si (111)-(√3×√3) surface with B-S5 configuration. Thin Ge layer growth on this structure has also been performed, and we found that no epitaxial growth could be achieved and the underneath structure was little disturbed.
Virtual interface method for in situ ellipsometry of films grown on unknown substrates
Authors: Urban F. K. , Tabet M. F.
Published: July 2002

In situ ellipsometry may be used for real time measurements on growing films through windows in deposition systems. It is well known that the initial film growth may be in the form of islands and other structures which may ultimately develop into a nearly homogeneous, isotropic growing film. Consequently, measurements in early growth phases do not agree with simple homogeneous, isotropic models which greatly complicates data reduction. A method is developed in which the refractive index and thickness of the overlayer can be computed without the need to consider the interface layer and substrate. Once the growth has passed the interface layer, a ‘‘virtual interface’’ is defined by a measurement at a point in time. Four additional measurements are made at subsequent times for computation of the optical properties of the growing overlayer film, four thicknesses (of growth past the virtual interface), and the complex reflection coefficients of the virtual interface. Results for Ni and Si films grown on BK7 glass substrates confirm the method.
Comparison of magnetron sputter deposition conditions in neon, argon, krypton, and xenon discharges
Authors: Petrov I. , Ivanov I. , Orlinov V. , Sundgren J.-E.
Published: July 2002

The ion and deposition fluxes to the substrate during sputtering of a vanadium target in neon, argon, krypton, and xenon discharges were measured as a function of the discharge power and gas pressure. The measurements of the deposition fluxes were also compared with calculations obtained using an analytical model for transport of the sputtered species through the gas discharge. The calculation takes into account both the ballistic and thermal components of the deposition flux. Overall, a good agreement between the calculated and the experimentally measured values was obtained. The results show that, at a constant discharge current, the vanadium flux at the substrate position is a strong function of both pressure and the type of inert gas used. The ion flux, on the other hand, remains relatively constant as the gas and pressure are changed. This implies that the ion-to-neutral arrival rate ratio was dominated by changes in the neutral deposition flux and it was found to increase with pressure, remain relatively constant with power at low pressures, and decrease with power at high pressures. By increasing the field strength of the outer pole in the magnetron source (unbalanced magnetron source of type II), the ion flux impinging the substrate was strongly increased for all pressures, while the vanadium deposition flux remained the same as in the ‘‘balanced’’ magnetron configuration.
Spontaneous etching of Si(100) by XeF2: Test case for a new beam surface experiment
Authors: Vugts M. J. M. , Joosten G. J. P. , van Oosterum A. , Senhorst H. A. J. , Beijerinck H. C. W.
Published: July 2002

An ultrahigh vacuum multiple-beam setup has been designed to study surface reactions that are of importance in plasma etch processes. The setup consists mainly of five beams (reactive neutrals, ions, electrons, CFx radicals, and photons) all of which can be focused on the same sample area, and a quadrupole mass spectrometer detecting only molecules desorbing from this area. Data are reported on spontaneous etching for the Si(100)/XeF2 system. Both the incident flux of XeF2 on the sample and the desorbing fluxes of SiFx products and nonused XeF2 were measured quantitatively. The reaction of XeF2, the production of SiFx species and the accumulation of fluorine on the silicon surface were studied as a function of temperature (300–900 K) for XeF2 fluxes of 0.24 and 1.04 monolayers/s. For the reaction probability of XeF2 an exponential increase with temperature from 11% at 300 K up to 50% at 900 K was found. The main product was found to be SiF4 at 300 K gradually becoming replaced by SiF2 at temperatures higher than 600 K. A remarkable result is the accumulation of a rather thick SiFx reaction layer on the etched surface. From thermal desorption spectra the fluorine content was calculated to be 38 monolayers at 300 K decreasing rapidly for higher temperatures. This suggests that fluorine diffusion into the silicon bulk might be of importance in the etching process.
Indium desorption from strained InGaAs/GaAs quantum wells grown by molecular beam epitaxy
Authors: Radhakrishnan K. , Yoon S. F. , Gopalakrishnan R. , Tan K. L.
Published: July 2002

The desorption and segregation of indium during molecular beam epitaxy growth of strained InGaAs/GaAs multiple quantum wells have been investigated by secondary ion mass spectroscopy (SIMS). The quantum wells were grown at various substrate temperatures, and the growths were interrupted at specified interfaces. Results indicate that indium desorption and segregation increase as the growth temperature is increased regardless of the type of growth interruption. However, the desorption was relatively high in the case of wells whose growths were interrupted at the top of the wells compared to the cases of bottom and no interruption, probably due to longer annealing of the exposed well surfaces at a high temperature. Similar results were obtained for the indium segregation. In all the cases, appreciable desorption starts only above 550 °C. SIMS results were analyzed using a simple rate-equation model for indium desorption, and the activation energy for indium desorption was found to be constant for both the top and bottom interrupted samples.
Kinetics and mechanism of plasma oxidation of tantalum silicides
Authors: Gómez-San Román R. , Pérez-Casero R. , Perrière J. , Enard J. P. , Martínez-Duart J. M.
Published: July 2002

Radio frequency (rf) plasma oxidation at the floating potential of tantalum silicides, TaSix (0.3≤x≤4.5), has been investigated. The oxidations were carried out in the 400–800 °C temperature range. Measurements of the overall oxygen (16O and 18O) and cation contents as well as their distribution in the films were carried out using Rutherford backscattering spectrometry and nuclear microanalysis techniques. The oxidation rate was found to be primarily controlled by the diffusion of the oxidizing species through the oxide. The influence of silicide composition, temperature, and substrate nature on the nature of the oxide has been analyzed. The rf plasma oxidation of TaSix silicides can be understood as the competition between two diffusion processes: oxygen diffusion from the plasma through the growing oxide and silicon migration from the silicide layer or from the silicon substrate. Both silicon and oxygen diffusion processes coexist and determine the nature of the grown oxide. The mechanisms of oxygen movement were studied using 18O as the tracer. The data show the maintenance of the order of oxygen atoms during oxide growth and a partial exchange of 16O present in the oxide with the 18O of the plasma. These results show that the microscopic mechanism of oxygen transport involves a short-range oxygen migration.
Study of electron-beam effects on trimethylsilane covered Si(100)
Authors: Ascherl M. V. , Campbell J. H. , Lozano J. , Craig J. H.
Published: July 2002

Electron-stimulated desorption (ESD) and temperature programmed desorption (TPD) studies were conducted on trimethylsilane dosed Si(100) surfaces. Experiments investigating the effects of electron-beam irradiation on TPD spectra and ESD kinetic energy distributions of hydrogen from trimethylsilane covered Si(100) surfaces are reported. Electron-beam irradiation strongly influences subsequent TPD spectra. Electron-beam induced dissociation of physisorbed particles on the surface is demonstrated. It is concluded that electron irradiation of trimethylsilane covered Si(100) selectively enhances or induces specific hydrogen adsorbed states when physisorbed species are present on the surface.
High performance Pirani vacuum gauge
Authors: Shie Jin-Shown , Chou Bruce C. S. , Chen Yeong-Maw
Published: July 2002

As an extension of previous work in our laboratory, a wide-range Pirani gauge that is capable of measuring vacuum pressure down to 10−7 Torr reproducibly has been built. The micromachined Pirani sensor used in the experiments has a suspended membrane that is supported by the nearly radiation-limited, thermally insulating beam leads crossing over a V-groove cavity. A method of partial dummy compensation, as proposed previously by Weng and Shie for eliminating the ambient drift, is proved here to be very effective with a thermal drift as small as only 5.7 μV/°C. It has also been found that a thermal-stress-induced piezoresistive effect, which has a profound influence on the limitation of measurement, appears in the constant-bias operation wherein the sensor temperature rises with the reduction of gas pressure and therefore thermal conduction. This effect causes the irreproducibility of pressure measurements by the device below 10−5 Torr. In addition to its inherently higher sensitivity, a constant-temperature circuit together with a thermoelectric stabilization of the sensor substrate temperature can eliminate the induced piezoresistive error. The constant-temperature circuit operating on the micro-Pirani sensor together with the above-mentioned temperature compensation and the stabilization methods have extended gauge capability down to 10−7 Torr, which is only limited by the signal readout resolution (∼1 μV). This is three orders of magnitude more sensitive than the conventional vacuum gauges of the thermal conductivity type.
Universal calibration of W5%Re vs W26%Re (type-C) thermocouples in the temperature range 32–2588 K
Authors: Smentkowski Vincent S. , Yates John T.
Published: July 2002

We provide a universal calibration of the W5%Re vs W26%Re (type-C) thermocouple alloy which may be used in the temperature range of 32–2588 K. Our calibration is within the limits of standard error reported by Omega [The Omega Complete Temperature Measurement Handbook and Encyclopedia (Omega Engineering, Stamford, CT, 1989), pp. z8–z28] for their data in the temperature range of 255–2588 K, and rationally extends the calibration downward in temperature.
Whiskers grown on aluminum thin films during heat treatments
Authors: Hinode Kenji , Homma Yoshio , Sasaki Yasushi
Published: July 2002

We studied whisker formation on aluminum (Al) films on silicon substrates during heat treatments, and investigated the influence of the aluminum film properties and the conditions of the heat treatment on whisker nucleation and growth. The whiskers, which were confirmed to grow in single crystals due to thermal stress, tended to form on films contaminated with oxygen and nitrogen. This is because these impurities suppress the Al film grain growth during heat treatment, causing localization of the film stress relief which results in whisker formation. Oxidizing the atmosphere during heat treatment suppresses the nucleation and growth of whiskers. This indicates that breaking Al surface oxide and/or atom rearrangement through surface diffusion has a critical role in the growth process of whiskers.
Effect of ion bombardment in very-high frequency glow discharge on growth and properties of SiHx films
Authors: Kosarev A. I. , Smirnov A. S. , Abramov A. S. , Vinogradov A. J. , Ustavschikov A. Yu. , Shutov M. V.
Published: July 2002

Ion and electron flow characteristics have been studied in different regimes both in rf (13.56 MHz) and VHF (58 MHz) glow discharges in silane. The measurements were conducted in a growth reactor and the data obtained was used for SiHx films deposition. Electronic properties of the films prepared under a variety of ion bombardment in rf, VHF discharges have been investigated. Correlation of these properties with ion parameters in rf, VHF discharges is discussed.
Thermal properties of perfluorinated n-alkanoic acids self-assembled on native aluminum oxide surfaces
Authors: Chen P. J. , Wallace Robert M. , Henck Steven A.
Published: July 2002

We have examined the thermal and chemical properties of a homologous series of long-chain perfluorinated n-alkanoic acids [CF3(CF2)nCOOH, n=8, 10, 12, 14, 16] self-assembled on native aluminum oxide surfaces using thermal desorption mass spectrometry and monochromatic x-ray photoelectron spectroscopy. These monolayers were prepared by solution self-assembly under ambient conditions on pre-cleaned native aluminum oxide surfaces and then transferred into an ultrahigh vacuum environment for surface analyses. A chemisorption bond strength of ∼30 kcal/mol between the reactive acid head group and the native aluminum oxide surface has been derived from thermal desorption studies. Upon increasing surface temperature, the predominant surface process was found to be molecular desorption. In addition, a minor surface chemical reaction channel also coexists at elevated temperatures, resulting in thermal dissociation of the long chain acid molecules and subsequent formation of a partially fluorinated aluminum oxide surface. These self-assembled molecular monolayers exhibit remarkable long-term ambient stability (∼103 h) which improves progressively with increasing fluorocarbon chain length.
Monolithic and multilayer Cr/CrN, Cr/Cr2N, and Cr2N/CrN coatings on hard and soft substrates
Authors: Kuruppu M. L. , Negrea G. , Ivanov I. P. , Rohde S. L.
Published: July 2002

Using controlled low-energy ion bombardment, CrN and Cr2N films were reactively sputtered from a Cr target in a mixed Ar-N2 discharge. Various Cr-N based coating architectures were developed in this work to provide better substrate accommodation than is currently available using monolithic CrN or Cr2N, as well as to build in “load support” for the hard surface layers on more compliant substrates. A series of monolithic and multilayer structures were deposited at low temperatures (<200 °C) to examine the advantages and disadvantages of various coating architectures and ion energies on three substrates: A2 tool steel, 52100 stainless steel, and 2024-aluminum. The optimal operating point for deposition of stoichiometric CrN and Cr2N coatings was determined from analysis of the target state, and supported by in situ ellipsometric measurement of the optical properties of the films during growth. Films were characterized using X-ray, scanning electron microscopy and Rutherford backscattering spectroscopy. Their properties have been evaluated by microhardness, scratch adhesion, and pin-on-disk wear testing. Many of the multilayer coatings gave microhardness values in excess of 2000 HK, often having better adhesion than the single layer films. This was reflected in the wear performance of these films on both A2 and 2024-Al, where no measurable wear was observed in severe dry sliding wear over sliding distances of more than 9000 m against a WC ball. Thus, wear-resistant Cr-N film architectures can be used on some temperature- sensitive and/or compliant substrates to significantly enhance their surface properties.
Ellipsomicroscopy for surface imaging: A novel tool to investigate surface dynamics
Authors: Haas G. , Pletcher T. D. , Bonilla G. , Jachimowski T. A. , Rotermund H. H. , Lauterbach J.
Published: July 2002

This article focuses on the technical issues of imaging of dynamic adsorbate pattern formation on platinum surfaces using laser light to illuminate the area of interest. In particular, ellipsomicroscopy for surface imaging (EMSI) is a powerful tool to follow spatio-temporal patterns of adsorbate layers on catalyst surfaces at arbitrary pressures. This novel method is uniquely sensitive to submonolayer coverages of adsorbates. It expands the range of observable pressure conditions by many orders of magnitude, thus bridging the pressure gap in imaging surface reactions. EMSI is a versatile technique that opens new avenues of potential applications to resolve dynamic surface processes, such as adsorbate diffusion or coating formation.
Polymerization of dual ion beam deposited CNx films with increasing N content
Authors: Ng Y. M. , Ong C. W. , Zhao X.-A. , Choy C. L.
Published: July 2002

Carbon nitride (CNx) films with 0–22.8 at. % N were prepared using dual ion beam deposition. With increasing N content in this range, more N-containing pyridinelike rings, and single, double, and triple bonds between C and N were formed, resulting in polymerization of the film structure. Consequently, the films became more transparent in the infrared region, and the hardness dropped from 24.2 to 12 GPa. Furthermore, nanoscratch tests showed that less debris was produced along the scratch track on the film containing high N content, indicating that the film was less brittle following the polymerization of the film structure. In addition, the minimum (critical) normal load for damaging the films dropped from 7.8 to 4 mN, reflecting that the adhesion between the films and substrates was weakened, thereby resulting in delamination of the films from the substrates. Finally, the room temperature electrical conductivity was found to be reduced by a factor of 100, consistent with the more pronounced polymerlike nature of the films at high N contents.
Innovation of the fore pump and roughing pump for high-gas-flow semiconductor processing
Authors: Akutsu Isao , Ohmi Tadahiro
Published: July 2002

A new screw pump has been developed as a useful backing pump for high-gas-flow semiconductor processing. The characteristic features of the screws are unequal lead and unequal slant angle, which realize higher pumping speed and smaller volume of the pumping system. This pump has a very wide dynamic range of 10−3–760 Torr with a high pumping speed and low electric power consumption by gradational lead screw structure and check valve at outlet. Furthermore, this pump is free from byproduct deposition, corrosion of inner surface and oil degradation. The backdiffusion of oils can be suppressed by admitting the N2 purge gas flow larger than 10 sccm to the inlet side of the pump.
Surface modification and cleaning enhancement of TaSi(N) films with dilute hydrofluoric acid
Authors: Mangat P. J. S. , Dauksher W. J. , Whig R. , O’Brien W. L.
Published: July 2002

Amorphous TaSi(N) alloy films are of great interest for application in the fabrication of reticles for next generation lithography and for incorporation into semiconductor devices as barrier layers for Cu processing. The stress characteristics of TaSi(N) films are critical when used as an absorber on x-ray and extreme ultraviolet lithography masks, or as a scatterer for electron projection lithography masks. One little understood, but critical characteristic of these films, is that they undergo a stress change towards a less tensile or more compressive state upon interaction with a buffered oxide etch (BOE). We have investigated the cause of this behavior using synchrotron radiation based high-resolution core level (Ta 4f and Si 2p) photoemission spectroscopy. Our results indicate that, upon interaction with a BOE, the surface oxide undergoes a major reorganization and the Ta gets heavily oxidized, resulting in the formation of Ta2O5. Such a reaction would lead to a buildup of strain in the oxidized region, which we interpret as being the contributing factor for the observed stress changes in the TaSi(N) thin films. Furthermore, annealing the surface results in a significant reduction of the oxide desorbtion temperature from 650 to 450 °C due to the HF interaction. This can be attributed to a change in the bonding configuration by HF, wherein the Si–O bonds are broken and weak Ta–O bonds are formed, causing the loosely bonded oxide to desorb at lower temperatures.
Effects of BCl3 addition on Ar/Cl2 gas in inductively coupled plasmas for lead zirconate titanate etching
Authors: An Tae-Hyun , Park Joon-Yong , Yeom Geun-Young , Chang Eui-Goo , Kim Chang-Il
Published: July 2002

The lead zirconate titanate (PbZrxTi1−xO3:PZT) ferroelectric thin films have received great attention for the applications on nonvolatile memory, infrared sensor, electro-optical device, microelectromechanical system device, etc. In order to accomplish the integration of these devices, the etching process for both PZT film and electrode material must be developed. In this study, PZT etching was performed using planar inductively coupled Ar(20)/Cl2/BCl3 plasma. The etch rate of PZT film was 2450 Å/min at Ar(20)/BCl3(80) gas mixing ratio and substrate temperature of 80 °C. X-ray photoelectron spectroscopy analysis for film composition was utilized. The chemical bond of PbO is broken by ion bombardment, and the peak of metal Pb in a Pb 4f peak begins to appear upon etching, decreasing Pb content faster than Zr and Ti. Also, the relative content of oxygen decreases rapidly. We thought that abundant B and BCl radicals made a volatile oxycompound such as BxOy and/or BCl–O bond. To understand the etching mechanism, Langmuir probe and optical emission spectroscopy analysis were utilized for plasma diagnostic.
Characterization and analysis of a novel hybrid magnetoelectronic device for magnetic field sensing
Authors: Schaadt D. M. , Yu E. T. , Sankar S. , Berkowitz A. E.
Published: July 2002

Structures in which magnetic and electronic materials are combined offer a variety of possibilities for realization of devices with improvement functionality or performance compared to conventional devices. We have designed, characterized, and analyzed a novel hybrid magnetoelectronic device: a monolithic field-effect-transistor-amplified magnetic field sensor in which a granular tunnel magnetoresistive (TMR) thin film, consisting of Co nanoparticles embedded in an insulating SiO2 matrix, is incorporated into the gate of a p-channel Si metal-oxide-semiconductor field-effect transistor. In this structure, current flow through the TMR film leads to a buildup of electronic charge within the gate due to the Coulomb charging energy of the Co nanoparticles, and consequently to a transistor threshold voltage shift that varies with applied external magnetic field. In a prototype demonstration device, the relative current change induced by application of a 6 kOe external magnetic field at room temperature was amplified from 5% for the current through the TMR film to 21% for the transistor subthreshold current. The absolute current response in the saturation regime increased by a factor of about 500 compared to that of the TMR film alone. A detailed analysis of the device operation and of methods for optimization of performance are presented. It is anticipated that substantially better performance should be achievable with relatively straightforward improvements in device design and processing. This device concept is shown to compare particularly favorably with Hall bar sensors and thus may be very beneficial in sensor applications for medium field ranges up to about 1 T.
Proximity correction for electron beam lithography using a three-Gaussian model of the electron energy distribution
Authors: Wind S. J. , Rosenfield M. G. , Pepper G. , Molzen W. W. , Gerber P. D.
Published: July 2002

Accurate proximity correction has proven essential for the patterning of submicron features using electron beam lithography. The use of a two-Gaussian model, which accounts for the finite beam size and forward scattering in the resist as well as backscattering, has demonstrated widespread success. It has been shown, however, that in certain instances, such as for features of order 100 nm or less or for exposure on high atomic number substrates, the two-Gaussian expression is unable to adequately fit the absorbed energy distribution in the resist. Suggested modifications, such as the addition of a third Gaussian term to account for large angle electron scattering, or the inclusion of an exponential term which may account for an increased absorption rate in high Z materials, have resulted in improved fits. This paper describes a study to determine the improvement gained in exposed features by including additional Gaussian terms in the expression for the absorbed energy distribution in the resist. A very high resolution probe (beam diameter ∼20 nm FWHM) is used so that forward scattering effects in the resist may be separated from the primary beam distribution. PMMA is exposed on Si and GaAs substrates at 25 keV using proximity correction parameters generated by curvefitting the three-Gaussian model and the two-Gaussian model to the absorbed energy distributions. The three-Gaussian model is seen to provide improved proximity correction particularly in the 100 nm size scale.
Asymmetry aberrations and tolerancing of complete systems of electron lenses and deflectors*
Authors: Liu Haoning , Zhu Xieqing , Munro Eric
Published: July 2002

The computation of asymmetry aberrations in electron-beam focusing and deflection system is discussed. The aberrations caused by the asymmetry errors (misalignment, tilt, and ellipticity) in magnetic and electrostatic defectors are especially emphasized. First, the method for evaluating the perturbations of electrostatic and magnetic fields due to the asymmetry errors are described; then the formulas for computing the asymmetry aberration coefficients are derived. A set of computer programs based on this paper and also our previous work [X. Zhu and H. Liu, in Proceedings of the International Symposium on Electron Optics, Beijing, 1986 (Institute of Electronics, Academia Sinica, Beijing, 1987), p. 309; E. Munro, J. Vac. Sci. Technol. B 6, 941 (1988); and H. Liu and X. Zhu, Optik 84, 123 (1990)] has been developed, which can handle the tolerancing of complete columns containing any combination of electrostatic and magnetic lenses and deflectors, such as are required for electron-beam lithography and inspection systems.
Plasma versus ozone photoresist ashing: Temperature effects on process-induced mobile ion contamination
Authors: Huynh Cuc K. , Mitchener James C.
Published: July 2002

Thin gate oxides used in metal-oxide-semiconductor devices are susceptible to mobile ion contamination introduced at critical patterning levels during photoresist stripping. Trace amounts of heavy, alkali metal ions such as sodium (Na+) and potassium (K+) that are found in even the best photoresists are very difficult to oxidize and do not form volatile products that can be easily removed in a typical O2 plasma. These ionic, heavy metals and their byproducts can be driven into critical underlying layers by self-induced bias potentials and positive ion bombardment within an O2 plasma environment. To examine this potential problem, a series of commercially available photoresist ashing systems were selected to study the influence of process-induced mobile ion contamination on sensitive underlying devices. The systems tested included a ‘‘downstream’’ rf plasma asher, a ‘‘downstream’’ microwave plasma system, and a nonplasma ozone ashing system. In this study, photoresist stripping rates and mobile ion (Ni) contamination levels were measured under various processing conditions for 125-, 150-, and 200-mm wafer substrates. Ashing rate measurements are detailed for the ozone ashing system and activation energies are calculated for ozone only and with the addition of nitrous oxide radical products to the ashing gas stream. Measured mobile ion contamination shows a strong temperature dependence for the ‘‘downstream’’ plasma ashing systems tested while the nonplasma, ozone ashing system showed no temperature dependence to process temperatures exceeding 300 °C and it was equal to the wet-chemical controls.
Nanomechanics and dynamics of tip–substrate interactions
Authors: Landman Uzi , Luedtke W. D.
Published: July 2002

The consequences of tip–substrate interactions are investigated using large-scale molecular dynamics simulations for a large (001) gold tip and a Ni(001) surface. The simulations reveal processes of adhesive contact formation upon approach of the tip to the substrate, tip elongation, and formation of an extended ordered neck upon retraction of the tip from contact, (111) reconstruction of the interfacial gold layers and the atomistic mechanisms of tip flattening and increase in contact area upon compression past the adhesive contact point. The hysteresis in the force versus tip to sample distance relationship, found upon approach and subsequent separation of the tip from the sample, is related to processes induced by adhesion and intermetallic bonding. The atomic-scale mechanisms underlying the jump-to-contact phenomenon at small tip to surface separation (∼4.2 Å) and of the inelastic processes and structural transformations involved in tip elongation, neck formation, and tip compression are discussed, and the results are compared to our earlier studies of a nickel tip interacting with a gold surface.
Erratum: ‘‘Momentum-space images of surface dimers on GaAs(001)-(2×4) by high-energy Auger and x-ray photoelectron diffraction’’ [J. Vac. Sci. Technol. B 10, 2092 (1992)]
Authors: Chambers S. A. , Loebs V. A. , Li Hua , Tong S. Y.
Published: July 2002

Due to an error in production, the top of Fig. 5 was inadvertently published upside-down. Figure 5 should have appeared as follows:
Momentum-space images of surface dimers on GaAs(001)-(2×4) by high-energy Auger and x-ray photoelectron diffraction
Authors: Chambers S. A. , Loebs V. A. , Li Hua , Tong S. Y.
Published: July 2002

We have obtained k-space images of As dimers in the surface layer of GaAs(001)-c(2×8)/(2×4) from the two-dimensional intensity maps of high-energy, core-level Auger, and x-ray photoelectron emission. The dimers are revealed as a major splitting in a small-angle scattering peak that is common to Ga 3d, 3p, 3s, and L3M4,5M4,5 intensity maps. This peak is of a rather complex origin, but the majority component is forward-focusing of Ga Auger and photoelectron waves generated in the fourth layer by As atoms in the surface layer. The splitting is caused by a change in symmetry in the surface layer resulting from dimer formation. Simple internuclear emitter-to-scatterer geometric modeling cannot be used to obtain the dimer bond length from the angles at which the two split-off features occur. Such modeling, which generates a reasonable quantitative estimate of the surface-structural parameters when the emitter and scatterer are nearest neighbors, fails in the present case because of the complex origin of this peak. Rather, quantum-mechanical scattering calculations carried out at either a kinematical or dynamical level are required to extract accurate surface-structural parameters. Fourier inversions of the angular intensity maps, which are essentially holograms of the surface, do not produce well-resolved dimer images in real space. This result is due to substantial contributions to the intensity map from emitters other than the one that produces the split peak in k space.
Metrology of high-resolution resist structures on insulating substrates
Authors: Di Fabrizio E. , Grella L. , Luciani L. , Gentili M. , Baciocchi M. , Figliomeni M. , Mastrogiacomo L. , Maggiora R. , Leonard Q. , Cerrina F. , Molino M. , Powderly D.
Published: July 2002

One of the main problems in the field of ultra-large-scale integration is the accurate use of metrological tools to provide information for critical dimension control of insulating material structures. In particular, for the inspection of high-resolution resist structures with a scanning electron microscope, it is necessary to choose the relevant working parameters, such as voltage and current, to take into account the electrical charging of the resist. Charging may influence the secondary electron (SE) signal that is used for metrology. In this article, the SE signal, collected while inspecting a resist structure on silicon substrates with an electron beam, is studied both theoretically and experimentally. Cold-cathode tungsten field emission microscopes, Hitachi S6100 and Hitachi S900, have been used for this study. Low-voltage signals are computed by direct simulation of low energy SE emission, using Monte Carlo (MC) calculations. The charging effect is evaluated as a function of beam energy and beam current for poly(methylmethacrylate) resist on a silicon substrate, by means of extensive calculations combining MC methods with the Poisson equation. The study of the signal profile is fundamental to the development of a precise metrological algorithm for high-resolution linewidth measurements. In previous articles calculations of the backscattered electron signal have been described from conducting materials derived using an analytical function that is the convolution of probe beam function and the specimen transfer function. In this work, the algorithm is extended to the SE signal obtained by e-beam inspection of insulating materials at voltages between 1 and 2 keV and currents of a few pA. It was found that linewidth variations are negligible for quarter micron structures when the working parameters, such as voltage and beam current, are chosen in accordance with MC calculations.
Chemical beam epitaxial growth of InP, InGaP, and InAs heterojunctions using triethylindium and bisphosphinoethane
Authors: Chin Albert , Martin Paul , Das Utpal , Mazurowski John , Ballingall Jim
Published: July 2002

The first chemical beam epitaxial growth of InP, InGaP/InP strained layer superlattices (SLS) and InGaP/InAs/InGaP quantum wells using bisphosphinoethane and tertiarybutylarsine as group V sources is reported. Mirrorlike surface morphology and excellent reflection high-energy electron diffraction patterns are observed. Room-temperature and 77 K Hall mobilities for a 2.0 μm thick InP epitaxial layer are 4200 and 22 000 cm2/V s, with carrier densities of 5.7E15 and 4.0E15 cm−3, respectively. The relatively low mobility is due to a high n-type impurity concentration at the epitaxial layer–substrate interface. The full width at half-maximum linewidth of the photoluminescence spectra are 0.84, 14.6, and 16.1 meV, for InP, InGaP/InP SLS, and InGaP/InAs/InGaP quantum well, respectively.
Molecular-beam epitaxy growth of quantum dots from strained coherent uniform islands of InGaAs on GaAs
Authors: Leonard D. , Krishnamurthy M. , Fafard S. , Merz J. L. , Petroff P. M.
Published: July 2002

The two- (2D) to three-dimensional (3D) growth mode transition during the initial stages of growth of highly strained InxGa1−xAs on GaAs is used to obtain quantum dot structures. Transmission electron micrographs (TEM) reveal that when the growth of InxGa1−xAs is interrupted exactly at the onset of this 2D–3D transition, dislocation-free islands (dots) of InGaAs result. Size distribution measurements from TEM images indicate that these dots are less than 300 Å in diameter and remarkably uniform. A phase diagram is constructed, showing the growth conditions under which these strained coherent uniform dots form. Photoluminescence from layers containing these dots is observed and correlated with growth conditions and with structural data obtained from TEM images. We observe that the photoluminescence emitted from the dots and an underlying reference quantum well are nearly equal, indicating a high quantum efficiency for these quantum dots.