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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films

Issue 4 • Date Jul 2003

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Displaying Results 1 - 25 of 130
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Transitional change to amorphous fluorinated carbon film deposition under energetic irradiation of mass-analyzed carbon monofluoride ions on silicon dioxide surfaces

    Page(s): L1 - L3
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    We have studied both the etching of SiO2 film and the growth of an amorphous fluorinated carbon (a-C:F) film by mass-analyzed fluorocarbon ion irradiation. This experiment was done in an ultrahigh vacuum with a pressure of 10-7 Pa even during irradiation. When using a carbon monoflouride (CF1+) ion with an energy of 300 eV to irradiate, it was found that SiO2 film a few nm thick was initially etched away. Then, an a-C:F film was continuously deposited on the SiO2 surface as the ion dose exceeded about 5×1016 cm-2. Using in situ x-ray photoelectron spectroscopy analysis, it was determined that carbon accumulates on the surface at this early stage as the ion dose increases, so that this transition is resulted by the surface modification on which the CF1+ ion itself irradiates the SiO2 surface. Especially in highly ionized fluorocarbon plasmas, surface conditions such as the carbon concentration affect possibly etching performance. © 2003 American Vacuum Society. View full abstract»

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  • Thermal stability and hydrogen atom induced etching of nanometer-thick a-Si:H films grown by ion-beam deposition on Si(100) surfaces

    Page(s): 831 - 837
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    Amorphous hydrogenated silicon (a-Si:H) films in the thickness range 0.1–4.5 nm were deposited on Si(100) surfaces at 350 K using the ion-beam-deposition method. The thermal stability of these a-Si:H films was studied by temperature programmed desorption spectroscopy. The films are stable up to 500 K, where a-Si:H starts to decompose via evolution of hydrogen (H2) and silane (SiH4). Approximately 99% of the hydrogen initially bound to the Si network was detected in the hydrogen channel. The hydrogen evolution peaks at ∼780 K caused by the decomposition of monohydride groups; the presence of SiH2 groups is indicated by hydrogen desorption below 700 K. The silane desorption states at 625 and 750 K reveal the existence of two different types of silyl (SiH3) groups. Etching of a-Si:H by impinging gas-phase H atoms was investigated in the temperature range from 150 to 700 K by in situ mass spectrometry. Silane was the sole etch product observed. The formation of silane proceeds via direct abstraction of silyl precursor groups by impinging hydrogen atoms, SiH3(a)+H(g)→SiH4(g); the silyl abstraction probability increases by a factor of 6 with increasing substrate temperature between 150 and 525 K. However, the steady-state erosion rate is controlled by the supply of silyl groups by successive hydrogenation of the Si network with the formation of SiH2 as bottleneck of the silyl supply. © 2003 American Vacuum Society. View full abstract»

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  • Photoluminescence of Mg-doped GaN grown by metalorganic chemical vapor deposition

    Page(s): 838 - 841
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    Two Mg-doped GaN films with different doping concentrations were grown by a metalorganic chemical vapor deposition technique. Photoluminescence (PL) experiments were carried out to investigate the optical properties of these films. For highly Mg-doped GaN, the PL spectra at 10 K are composed of a blue luminescence (BL) band at 2.857 eV and two excitonic luminescence lines at 3.342 eV and 3.282 eV, in addition to a L2 phonon replica at 3.212 eV. The intensity of the L1 line decreases monotonously with an increase in temperature. However, the intensity of the L2 line first slowly increases at first, and then decreases quickly with an increase in temperature. The two lines are attributed to bound excitonic emissions at extended defects. The BL band is most likely due to the transition from deep donor Mg–VN complex to Mg shallow acceptor. From the temperature dependence of the luminescence peak intensity of the BL band, the activation energy of acceptor Mg was found to be 290 meV. © 2003 American Vacuum Society. View full abstract»

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  • Energetic deposition of niobium thin film by ecr-plasma

    Page(s): 842 - 845
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    An electron cyclotron resonance (ECR)-plasma reactor has been built to do energetic ion deposition of refractory metals in vacuum. The system uses an E-beam gun to create refractory metal flux. The neutral metal flux feeds into a microwave resonator and forms pure metal plasma created by electron cyclotron resonance. The metal ions are extracted to a biased substrate for direct deposition. A retarding field energy analyzer is developed and used to measure the kinetic energy of metal ions at the substrate location. A high-quality niobium thin film is obtained through this deposition system. The niobium film exhibits an excellent superconducting transition. The niobium ion energy distribution has been measured. The niobium ion at the substrate location has a median kinetic energy of 64 eV with an energy spread of 20 eV under certain plasma conditions. © 2003 American Vacuum Society. View full abstract»

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  • Effect of sputtering pressure on residual stress in Ni films using energy-dispersive x-ray diffraction

    Page(s): 846 - 850
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    A procedure for determining the residual stress in thin films using energy dispersive x-ray diffraction was investigated. The effect of the sputtering pressure on the residual stress in dc magnetron sputtered Ni films was studied in greater detail using this approach. The behavior reported suggested the possibility of controlling or influencing the sign and/or magnitude of the residual stress. In addition, the stress variation with increasing negative bias voltage is also presented. In the range studied, between -15 and -150 V, residual stress is always tensile. © 2003 American Vacuum Society. View full abstract»

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  • Structural and mechanical properties of diamond-like carbon films deposited by direct current magnetron sputtering

    Page(s): 851 - 859
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    The microstructure, morphology, and mechanical properties of diamond-like carbon (DLC) films deposited by direct current magnetron sputtering were investigated for microelectromechanical systems applications. Film properties were found to vary markedly with the ion energy (Eion) and ion-to-carbon flux ratio (Jion/JC). Cross-sectional high-resolution transmission electron microscopy revealed an amorphous microstructure. However, the presence of nanometer-sized domains at Eion∼85 eV was detected. Film stresses, σ, which were compressive in all cases, ranged from 0.5 to 3.5 GPa and depended on the flux ratio as well as ion energy. The hardness (H), Young’s moduli (ε), and elastic recovery (R) increased with Eion to maximum values of H=27 GPa, ε=250 GPa, and R=68% at Eion=85 eV and Jion/JC=4.4. However, near edge x-ray absorption fine structure and electron energy-loss spectrum analysis showed that the sp2/sp3 content of the films does not change with Eion or Jion/JC. The measured change in mechanical properties without a corresponding change in sp2/sp3 ratio is not consistent with any previously published models. We suggest that, in the ranges 5 eV ≤Eion≤85 eV and 1.1 ≤Jion/JC≤6.8, the presence of defective graphite forme- - d by subplanted C and Ar atoms has the dominant influence on the mechanical properties of DLC films. © 2003 American Vacuum Society. View full abstract»

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  • X-ray photoemission spectra and x-ray excited Auger spectrum investigation of the electronic structure of Pd3(PS4)2

    Page(s): 860 - 865
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    Information on the bonding states of the compositional atoms and on the occupied energy states of the Pd3(PS4)2 crystals have been obtained by investigating the Pd 3d and P and S 2p core levels and the valence band region with the x-ray photoemission spectroscopy. In particular, as far as core levels are concerned, each XPS spectrum, apart from the spin-orbit splitting, exhibits a single-peak structure suggesting the absence of nonequivalent sites for the compositional atoms. The analysis of the chemical shifts in the core-level binding energies of the constituents emphasizes their cation or anion-type behavior. As to the valence band (VB) XPS spectrum, two regions are distinguished and interpreted on the basis of the comparison with the VB XPS spectra of other palladium and (PS4)3- compounds and of some thiophosphates. Confirmation of an involvement of the Pd 4d in the bonding is also given by the analysis of the spectral shape of the x-ray induced Pd M45VV Auger transition. © 2003 American Vacuum Society. View full abstract»

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  • Laser desorption time-of-flight mass spectrometry of fluorocarbon films synthesized by C4F8/H2 plasmas

    Page(s): 866 - 873
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    Molecular structures of fluorocarbon films synthesized by C4F8/H2 plasmas were analyzed by laser desorption time-of-flight mass spectrometry (LD-TOFMS). Mass peaks of positive and negative ions with m/z up to 250 were observed in the mass spectra. Most of these ions were assigned as atomic hydrogen, atomic fluorine, carbon clusters, hydrocarbon clusters, fluorocarbon clusters, and hydrofluorocarbon clusters. The mass spectra changed sensitively with the partial pressure of H2. The LD-TOFMS analysis showed that the films changed from a polytetrafluoroethylene-like film into crosslinked carbon- and hydrogen-rich one by the addition of H2. The change in the chemical composition of the mass spectrum was consistent with the analyses by conventional x-ray photoelectron spectroscopy and Fourier transform infrared absorption spectroscopy. It is emphasized that LD-TOFMS can be used for the analysis of the degree of polymerization, which is an advantage of LD-TOFMS over the conventional analysis methods. © 2003 American Vacuum Society. View full abstract»

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  • Pulsed laser ultrahigh vacuum deposited silicon in the presence of excess cesium and oxygen studied with x-ray photoelectron spectroscopy and atomic force microscopy

    Page(s): 874 - 880
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    Si/Cs/O clusters were prepared in an ultrahigh vacuum system with pulsed laser ablation of Si in the presence of Cs vapor and molecular oxygen. The effects of an O2 ambient, the pressure, and the deposition sequence of Cs and O2 on the oxidation state of cesium oxides and silicon oxides, as well as on the formation of Si/Cs/O clusters, were studied with x-ray photoelectron spectroscopy and atomic force microscopy (AFM). Oxygen 1s spectra were deconvoluted to cesium oxide(s) at around 530.5 eV and silicon oxide(s) at 532.3 eV. From the low binding energy side to the high binding energy side, Si 2p spectra were assigned to negatively charged Si clusters (94 and 96 eV), silicon suboxide (102 eV), SiO2 (104 eV), and Si/Cs/O clusters (106 eV), respectively. The high binding energy species was explained by the formation of Si(CsO1+x)n clusters. Surface morphologies were influenced by the oxidation state of cesium oxides and their amount. The work function decrease as much as 0.5±0.1 eV was measured with ex situ AFM. © 2003 American Vacuum Society. View full abstract»

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  • Edison’s vacuum technology patents

    Page(s): 881 - 891
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    During 1879 Thomas Edison’s Menlo Park, New Jersey laboratory developed the means to evacuate glass lamp globes to less than a mTorr in 20 min and in mid-1880 began production of carbon-filament incandescent lamps. Among Edison’s nearly 1100 U.S. patents are five for vacuum pump improvements, and at least eight others that are vacuum-related; all applied for between 1880 and 1886. Inspired by an 1878 article by De La Rue and Müller [Philos. Trans. R. Soc. London, Ser. A 169, 155 (1878)] on studies of glow discharges, Edison devised a combination pump using the Geissler pump as a rough pump and the Sprengel pump for continuous exhaustion. Edison’s patents described means to control the mercury flow and automate the delivery of the mercury to banks of up to a hundred pumps. Other patents described various means to remove residual gases during lamp processing. © 2003 American Vacuum Society. View full abstract»

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  • Low temperature pulsed etching of large glass substrates

    Page(s): 892 - 894
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    Glass plates of 20 cm diameter have been etched by SF6 in a pulsed capacitively coupled 13.56 MHz discharge. The plates were mechanically clamped to the cooled substrate holder and allowed to heat due to ion bombardment. The average rf power was set at 220 W and the pulse frequency varied up to 200 kHz for duty cycles between 10% and 100%. For a pressure of 50 mTorr, pulse frequencies around 100 kHz and duty cycles below 30%, the etch rate was about double that of the continuous case and the glass plate temperature was between 90 and 100 °C about 30° below the continuous case. These results show that large plates of glass can be etched rapidly at 0.16 μm per minute at temperatures below the cross linking temperature of a photoresist mask. © 2003 American Vacuum Society. View full abstract»

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  • Effects of Si addition on the microstructural evolution and hardness of Ti–Al–Si–N films prepared by the hybrid system of arc ion plating and sputtering techniques

    Page(s): 895 - 899
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    Ti–Al–Si–N films were deposited on WC–Co substrates by the hybrid coating system of arc ion plating method for Ti–Al sources and dc magnetron sputtering technique for Si incorporation. The synthesized Ti–Al–Si–N films were revealed as composites of solid-solution (Ti,Al,Si)N crystallites and amorphous Si3N4 by instrumental analyses such as x-ray diffraction, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The Si addition in Ti–Al–N films affected the refinement and uniform distribution of crystallites by percolation phenomenon of amorphous silicon nitride similar to that of the Si effect in TiN film. The solubility limit of Si in the Ti0.76Al0.24N crystal is believed to be about 6 at. %. No free Si was observed due to the very high ionization rate of nitrogen gas in the arc plasma. As the Si content increased up to about 9 at. %, the hardness of Ti–Al–N film steeply increased from 30 GPa to about 50 GPa. Ti–Al–Si–N films having the maximum hardness showed the nanocomposite microstructure consisting of fine (Ti,Al,Si)N crystallites, about 8 nm in size, dispersed uniformly in the amorphous Si3N4 matrix. © 2003 American Vacuum Society. View full abstract»

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  • Plasma-enhanced chemical vapor deposition of SiO2 from a Si(CH3)3Cl precursor and mixtures Ar/O2 as plasma gas

    Page(s): 900 - 905
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    Silicon dioxide thin films have been prepared at room temperature by remote plasma-enhanced chemical vapor deposition in a downstream reactor by using Si(CH3)3Cl as a volatile precursor and a microwave electron cyclotron resonance external source. Experiments are done at constant pressure by changing the relative amount of Ar species R in the plasma gas. The aim was to obtain thin films with low density and, therefore, low refractive index. Characterization of the species of the plasma is carried out by optical emission spectroscopy. The changes of the plasma conditions are correlated with the growing rate and microstructure of the films, the latter determined by atomic force microscopy and infrared spectroscopy. It is found that the growing rate of the films decreases and their roughness increases as R increases. The optical properties of SiO2 thin films are analyzed by optical ellipsometry. A decrease in the refractive index is found for the films grown with high values of R. The possible routes for activation of the precursor and the formation of the SiO2 thin films are discussed. © 2003 American Vacuum Society. View full abstract»

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  • Microstructural and optical properties of aluminum oxide thin films prepared by off-plane filtered cathodic vacuum arc system

    Page(s): 906 - 910
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    Transparent, amorphous, surface smooth, and hard aluminum oxide thin films were deposited on Si (100) and quartz substrates by an off-plane filtered cathodic vacuum arc (FCVA) system. We systematically studied the optical properties, such as transmittance and optical constants, of the aluminum oxide thin films deposited under various oxygen partial pressures. Experimental results show that the optical properties for aluminum oxide thin films are strongly dependent on oxygen partial pressure; the higher oxygen partial pressure causes much more oxygen to incorporate into the film thus inducing more modification of film properties. At proper oxygen partial pressure, the stoichiometric alumina film is obtained, which is smooth and dense. Additionally, it also displays good optical properties with a refractive index of ∼1.7 at 550 nm. The properties exhibited by the alumina thin films manifest the potential applications for alumina thin films in optical coatings and for FCVA technology in deposition of metal oxide optical films. © 2003 American Vacuum Society. View full abstract»

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  • Feature profile evolution in high-density plasma etching of silicon with Cl2

    Page(s): 911 - 921
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    A Monte Carlo based profile simulator was constructed that incorporated the dominant reaction mechanisms of surface chlorination under simultaneous neutral and ion bombardment, surface etching, and ion reflection. The profile simulation is based on the kinetics model developed from beam studies that measured the ion energy, ion and neutral fluxes and ion angular dependencies of Cl+ ion-enhanced etching with Cl. The profile evolution of patterned samples with oxide hard mask etched in an inductively coupled plasma etcher were simulated. The mechanisms of undercutting and microtrenching forming were discussed. Ions scattered from the neighboring hardmask were primarily responsible for the undercutting, while ions reflected from bowed feature sidewalls were primarily responsible for the microtrenching. The profile evolutions under different processing conditions were compared with experimental results and some etching artifacts were characterized and discussed. The neutral-to-ion ratio was found to influence the surface chlorination significantly, thus causing variation of profile evolution. Higher ion energy would give more ideal profiles due to increased ion directionality. However, higher ion energy also increased the etching rate and reduced the chlorination at the bottom of the feature. The reduced chlorination of the feature bottom relative to the sidewall increases the ratio of lateral etching to vertical etching, and decreases the etching anisotropy. The influence of SiCl2 deposition and mask angle on feature profile evolution were also investigated. © 2003 American Vacuum Society. View full abstract»

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  • Determination of Ti+-flux and Ar+-flux of ionized physical vapor deposition of titanium from multiscale model calibration with test structures

    Page(s): 922 - 936
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    In this article we determine physical parameters characterizing the ionized physical vapor deposition of titanium in a Hollow Cathode Magnetron by comparing experimental results obtained from suitable submicron test structures with a multiscale model. The model includes the reactor scale, the plasma sheath and presheath scale, and the feature scale. The reactor scale model delivers the energy and angular distribution of the neutral sputtered particles from the reactor geometry and an energy dependent collision model. The sheath and presheath model calculates the energy and angular distribution of the ions from the reactor model and a subsequent scattering model describes collisions in the presence of magnetic fields. The levelset-based feature scale simulator propagates the front according to local growth velocities which are calculated from Monte Carlo particle flux and reaction kinetics (derived from molecular dynamics calculation). The calibration is performed in two steps with help from bottle-shaped test structures as well as technologically relevant structures. First, hi-fill and ultra-hi-fill magnetron sputter processes of titanium are investigated in order to verify the transport model for the neutral particles. Second, a Hollow Cathode Magnetron sputter process of titanium is analyzed in order to verify the transport model for postionized particles. This analysis is performed for a floating substrate process and a process with rf-driven substrate bias. The postionized flux fraction of titanium in this technology is not calculated from a plasma model but treated as a free parameter. The prediction of the model and the comparison with the experimental data allow us to determine this value as 0.7±0.1 under a standard condition. The ionized flux of argon relative to the ionized flux of titanium is determined as 2. The results show that the bottom and sidewall coverage of the process depends significantly on the angular dependence of the- - ionized component which is essentially a result of processes in the presheath. The validity of the model covers a variety of plasma and process conditions. It can be applied to other reactor concepts and materials. © 2003 American Vacuum Society. View full abstract»

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  • Comparison of the stability of hot and cold cathode ionization gauges

    Page(s): 937 - 946
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    When ionization gauges are used as reference or secondary standards, their stabilities are the most important features. Generally, only hot cathode gauges are used as reference or secondary standards in calibration services. Some traditional reasons preventing the use of cold cathode gauges are the presence of discontinuities in the current versus pressure characteristic, the ignition delay at very low pressures, and the poor stability especially under contaminating vacuum environments. Though current inverted magnetron designs are believed to avoid some of these problems, at least under clean conditions, no “hard facts” have been published to support this claim. Here, we present the experimental results of calibrations of three hot cathode gauges and two inverted magnetrons against a primary high-vacuum standard over the range 10-7 to 10-3Pa with gases of N2, Ar, He, and H2, respectively. During a continuous observation period of 72 h at a constant pressure of about 1×10-4Pa, hot cathode gauges showed better stabilities than inverted magnetrons in N2, Ar, and He, but all gauges behaved similarly in H2. Repeated calibrations over a period of about 6 months showed that all gauges had similar long-term stabilities in N2, Ar, and He. For H2, however, the stability of inverted magnetrons was better than that of hot cathode gauges. For different gases, the discontinuities of inverted magnetrons occurred at different pressures, making their calibrations more elaborate. © 2003 American Vacuum Society. View full abstract»

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  • Mechanism of hardening in Cr–Al–N–O thin films prepared by pulsed laser deposition

    Page(s): 947 - 954
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    Chromium aluminum oxynitride (Cr–Al–N–O) thin films have been prepared by pulsed laser deposition. Experiments were carried out by changing the surface area ratio of targets [SR=SAlN/(SCr2N+SAlN)] from 0% to 100%. The composition of the thin film prepared at SR=75% was determined to be Cr0.11Al0.39N0.25O0.25 by Rutherford backscattering spectroscopy. From the result of grazing angle x-ray diffractometry, the phase transition of the Cr–Al–N–O thin films was clarified to occur, when the aluminum content in cations (x) ranged from 70 to 90 at. %. In addition, the thin films having composition close to the solubility limit were observed by transmission electron microscopy to contain chromium nitride particulates below 200 nm in diameter. The Cr–Al–N–O thin film with x=25 at. %, which was the hardest over the whole x range, had Vickers hardness above 4000. In this thin film, nanometer-sized crystallites were found in the grains. Moreover, the elastic modulus was shown to be higher than those of other Cr–Al–N–O thin films. © 2003 American Vacuum Society. View full abstract»

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  • Etching silicon by SF6 in a continuous and pulsed power helicon reactor

    Page(s): 955 - 966
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    The etch rate of silicon by SF6 in a helicon reactor has been measured along with simultaneous actinometric measurements of the concentration of atomic fluorine in the gas phase for a variety of gas flow rates resulting in pressures in the mTorr range. A bias rf power was applied to the substrate to investigate the effect of ion energy on the etch rate. The etch rate was found to be proportional to the fluorine concentration and independent of the bias for the higher gas flow rates. However, at lower flow rates, the situation was more complicated and no simple model can explain the measurements. Measurements of the etch rate were also made in the afterglow of a repetitively pulsed discharge so that the directed ion energy would be reduced to the thermal motion after the rapid collapse of the plasma potential. A simple model was developed to explain the temporal etching phenomena in terms of the lifetime of the atomic fluorine. © 2003 American Vacuum Society. View full abstract»

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  • X-ray diffraction study of residual stresses and microstructure in tungsten thin films sputter deposited on polyimide

    Page(s): 967 - 972
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    Structural and mechanical properties of metal/polymer systems are of great interest for technological applications since they strongly influence the quality and lifetime of these systems. The phase composition, microstructure, and residual stresses of tungsten films sputter deposited on polyimide substrates have been analyzed by x-ray diffraction. The influence of several deposition parameters is studied. In 200 nm thick films, the tungsten β phase is observed when oxygen incorporation is high. As the film thickness increases, a thermally activated β→α phase transition occurs and only the α phase exists in the 600 nm films. High compressive residual stresses are evidenced in both phases. © 2003 American Vacuum Society. View full abstract»

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  • Standards for surface analysis: ASTM committee E-42 on surface analysis

    Page(s): 973 - 978
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    Surface analysis is of critical importance to most of the Divisions of the American Vacuum Society and has been one of the most dynamic scientific and technological growth areas for the last 30 yr. The ASTM Committee E-42 on Surface Analysis was formed in 1976 to help advance the quality of surface analysis by developing appropriate standards (reference materials, reference data, and reference procedures), and by leading round robin comparisons, preparing publications, and holding symposia and workshops. A major function of the committee has been the development of standards and reference procedures. This article is a description of the organization of Committee E-42, and a summary of recent activities by this volunteer group with an emphasis on the processes used, a description of standards published, and standards that are being developed by Committee E-42 and other international organizations. © 2003 American Vacuum Society. View full abstract»

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  • Raman and photoluminescence of ZnO films deposited on Si (111) using low-pressure metalorganic chemical vapor deposition

    Page(s): 979 - 982
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    The highly c-oriented ZnO films were epitaxially grown on n-type Si (111) substrate at the temperature range of 340–460 °C using the low-pressure metalorganic chemical vapor deposition method. All films exhibit a pronounced (002) peak for ZnO, indicative of the strong c-axis oriented characteristic. The ZnO film grown at 400 °C shows the best structural quality along with the largest lateral grain size, well supported by the narrowest full width at half maximum of ZnO (002) peak about 0.19° in x-ray diffraction. However, the temperature dependence of the vibrational modes at 436 and ∼563 cm-1 in Raman spectra revealed a low density of oxygen vacancies in the films grown at low temperatures, which is supposed to determine the photoluminescence (PL) properties. At low temperatures, the narrow ultraviolet (UV) near band emission dominated the PL spectrum with a very weak low energy tail near the band. High temperature (up to 460 °C) would cause serious oxygen deficiency, resulting in the weak broad UV band with obvious blue band emission. © 2003 American Vacuum Society. View full abstract»

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  • Surface morphology and dynamic scaling in growth of iron nitride thin films deposited by dc magnetron sputtering

    Page(s): 983 - 987
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    Iron nitride films were deposited by dc magnetron sputtering using an Ar/N2 gas mixture. The structure, roughness, and surface morphology of the films were investigated using x-ray diffraction, grazing incidence x-ray scattering (GIXS), and atomic force microscopy (AFM). It was found that the morphologies and structures of the films were influenced by the N2 fraction. The perpendicular fluctuations in the height h(x,t) of the surface were also analyzed by AFM and GIXS in the light of dynamical scaling approach. The surfaces of the films typically exhibited self-affining structures both in space and in time. The two dependent nontrivial exponents, roughness exponent α and growth exponent β, were determined. For the iron nitride films grown at N2 fraction of 5%, 10%, and 30%, α≈0.65, 0.56, and 0.39, and β≈0.53±0.02, 0.38±0.02, and 0.29±0.03, respectively. The scaling relationship α+α/β≈2 is obeyed in all samples, which is in agreement with Kardar–Parisi–Zhang universality. The discrepancies between the theoretical foundations of dynamic scaling and experimental results have been discussed as well. © 2003 American Vacuum Society. View full abstract»

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  • Ionic densities and ionization fractions of sputtered titanium in radio frequency magnetron sputtering

    Page(s): 988 - 993
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    Ionic densities of sputtered titanium (Ti) in rf magnetron sputtering were measured using an optical absorption method. Measurements of ionic densities of sputtered Ti were made by varying pressure of Ar gas, applied rf power and distance from the target. The densities of Ti atoms were measured using an atomic absorption method for deriving ionization fraction of sputtered Ti. At the rf power of 200 W, ionic densities of Ti were found to be lower than 1.0×1010cm-3 indicating that ionization fractions were of the order of several percentages at Ar pressures lower than the pressure of several Pascals that is used in conventional sputtering. The ionic density increased with increasing pressure and reached a maximum value of 4.8×1010cm-3 at the Ar pressure of 21 Pa for z=15 mm where z is axial distance with origin at the Ti target surface. Also, both ionic and atomic densities of sputtered Ti increased monotonically with increasing rf power resulting in an almost constant value of ionization fraction at the Ar pressure of 7 Pa. Probe measurements indicated that fractions of Ti ion were around 30%–40% of the total ionic density which at pressures higher than several Pa was mainly made up of Ar ion. The ionization rate of electron impact for Ti and Ar is discussed based on measurements made by the authors. © 2003 American Vacuum Society. View full abstract»

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Aims & Scope

The Journal of Vacuum Science and Technology A is devoted to reports of original research, review articles, and Critical Review articles.

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Editor
G. Lucovsky
North Carolina State University