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

Issue 4 • Date Jul 1998

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Displaying Results 1 - 25 of 119
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Residual stress in low pressure chemical vapor deposition SiNx films deposited from silane and ammonia

    Page(s): 2003 - 2007
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    Varied SiNx films have been deposited by low pressure chemical vapor deposition from silane SiH4 and ammonia NH3 and the influences of the deposition parameters (temperature, total pressure and NH3/SiH4 gaseous ratio) on the film deposition rate, refractive index (assessed at a 830 nm wavelength), stoichiometry and thermomechanical stress are investigated and correlated. Low stress (≈600 MPa) Si3N4 films are obtained for the highest deposition temperature and the lowest total pressure but the gaseous ratio is shown to be the dominant parameter. According to the SiNx stoichiometry, silicon-rich silicon nitride and nitrogen-doped silicon (called NIDOS) depositions are obtained and compressive to tensile stresses are reported. A maximum in compressive stress is put into evidence for N/Si ratio roughly equal to 0.7 and is related to the cumulated effects of silicon nitridation and crystallization, characterizing the transition between nitrogen-doped silicon and silicon-rich silicon nitride. Finally, by considering stress, deposition rate, nonuniformity along the load and resistance to alkaline solutions, optimal (silicon-rich) silicon nitride deposition conditions are proposed for microelectromechanical applications. © 1998 American Vacuum Society. View full abstract»

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  • Plasma cleaning and nitridation of sapphire substrates for AlxGa1-xN epitaxy as studied by x-ray photoelectron diffraction

    Page(s): 2008 - 2015
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    The influence of plasma and thermal treatments on the structure and composition of sapphire (00.1) surfaces has been studied by hemispherically recorded x-ray photoelectron spectroscopy and diffraction (XPD) to better understand the surface conditioning during the growth initiation procedure for the epitaxy of GaN. A treatment involving an O2 plasma generated by electron cyclotron resonance is shown to efficiently remove surface contamination and to produce well-ordered surfaces. After a thermal treatment in vacuum the sapphire (00.1) surface becomes terminated by Al atoms. AlN films with good short-range order are obtained by a simple high temperature nitridation step in the metal organic chemical vapor deposition reactor. A novel direct crystallographic method termed CHRISDA is employed for the analysis of the XPD data. By analysis of the XPD patterns the crystal structure of sapphire is found to extend into the probed near surface region without significant perturbations. The AlN layers formed by thermal nitridation were found to crystallize in the hexagonal phase and to be terminated by nitrogen atoms. © 1998 American Vacuum Society. View full abstract»

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  • Application of a toroidal plasma source to TiN thin film deposition

    Page(s): 2016 - 2020
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    A toroidal plasma source for plasma deposition at the University of Sydney (PLADEPUS) has been developed for studies of deposition of thin films, such as titanium nitride (TiN). This article describes measurements of the plasma parameters at a low rf power input, the experimental setup of the preliminary thin film deposition and the method of titanium (Ti) atom injection into the plasma by using a small current Ti arc. The microstructure of the TiN thin films is analyzed and the results are presented. © 1998 American Vacuum Society. View full abstract»

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  • Plasma-deposited silicon oxide and silicon nitride films on poly(ethylene terephthalate): A multitechnique study of the interphase regions

    Page(s): 2021 - 2030
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    The “interphase” region between the deposited layer [e.g., plasma-enhanced chemically vapor deposited (PECVD) SiO2 or SiN] and the poly(ethylene terephthalate) (PET) substrate has been investigated and compared to physical vapor deposited (PVD) (electron beam evaporated) SiO2. Composition profiles determined by time-of-flight elastic recoil detection, electron microprobe analysis, and x-ray photoelectron spectroscopy all show an extended interphase region more than 50 nm in width, while the profile of the PVD SiO2 is narrower. However, since these analytical techniques are invasive and prone to artifacts, we have also examined ultrathin (about 10 and 20 nm) SiO2 and SiN PECVD layers on 50 nm spin-coated PET substrates by nondestructive infrared (IR) techniques. The IR spectra confirm that the thin PECVD deposits also comprise an organosilicon phase with Si–CHx bonds. We explain these observations in terms of a fragmentation/redeposition mechanism: During the earliest stage of PECVD, interaction between the plasma and the polymer surface produces volatile organic species, which intermix with the reagent gas feed, thus giving rise to the observed organosilicon-like deposit with gradually decreasing carbon content. © 1998 American Vacuum Society. View full abstract»

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  • Reactive ion etching for AlGalnP/GaInP laser structures

    Page(s): 2031 - 2036
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    To fabricate the AlGaInP/GaInP strained-multiple-quantum well laser, the reactive ion etching of GaAs, GaInP, AlGaInP, and AlInP in BCl3/Ar discharges was investigated as a function of plasma parameters such as power, pressure, gas flow rate, and reactive composition, as well as etching time. Photoluminescence and Auger electron spectroscopy measurements were used to characterize the damage and surface residues caused by reactive ion etching. We have achieved a highly selective etching of GaAs with underlying GaInP. Selective etching of GaInP with AlInP and a smooth etching surface were also achieved. © 1998 American Vacuum Society. View full abstract»

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  • Reactive ion etching of piezoelectric materials in CF4/CHF3 plasmas

    Page(s): 2037 - 2041
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    The reactive ion etching of substrates used in piezoelectric devices (quartz, fused silica, LiNbO3, LiTaO3, and sapphire) has been characterized in CHF3/CF4-based plasmas. For quartz and fused silica, a regime of ion-enhanced chemical etching similar to that established by Steinbruchel [Ch. Steinbruchel, J. Electrochem. Soc. 130, 648 (1983)] for CF4 was indicated over the range of compositions from CF4=1 to CHF3=1. In this regime, the etch rate was dependent on the square root of the rf bias voltage (V1/2). The etch rate of both the quartz and fused silica was at a maximum in a CF4 plasma and decreased continuously with an increase in the ratio of CHF3/CF4 gases in the mixture. In comparison, the etch rates of LiNbO3, LiTaO3, and sapphire were invariant with changes in the ratio of the CHF3/CF4 gases, the flow rate, and the chamber pressure. The constancy of etch rate in these substrates has been attributed to a predominance of etching by a physical process of sputtering. © 1998 American Vacuum Society. View full abstract»

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  • Deposition and characterization of gold thin films on Si by CF4+O2 gas microwave plasma

    Page(s): 2042 - 2046
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    Thin films of Au deposited on Si[(100), n type] wafers using a solid Au source and CF4+O2 microwave plasma were studied. Solid Au heated at 200 °C in a vacuum crystal reactor was vaporized in a CF4+O2 microwave (2.45 GHz power 200 W) plasma flow, and the Au film was deposited on a Si wafer heated to 270 °C in a low-pressure (10 mTorr) O2 atmosphere. The density of Au in this film was about 91.7% as analyzed by x-ray photoelectron spectroscopy, and the film resistivity was 2.8 μΩ cm, which is almost the same as that of the initial bulk Au (2.4 μΩ cm). The deposition mechanism was deduced. The heated solid Au reacts with O2 and (CF2)n from the CF4+O2 microwave plasma, and then the Au is converted into AuO(CF2)n. This Au compound carries Au atoms to the vacuum chamber. In the O2 atmosphere, vaporized AuO(CF2)n is oxidized and changed into oxides such as AuO and COFx. AuO is deposited on the Si wafer heated to 270 °C, and then reduced into Au and O2 by heating. This process results in a high purity deposited gold film. © 1998 American Vacuum Soci- - ety. View full abstract»

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  • Remote plasma etching of silicon nitride and silicon dioxide using NF3/O2 gas mixtures

    Page(s): 2047 - 2056
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    The etching of silicon nitride (Si3N4) and silicon dioxide (SiO2) in the afterglow of NF3 and NF3/O2 microwave discharges has been characterized. The etch rates of both materials increase approximately linearly with the flow of NF3 due to the increased availability of F atoms. The etch rate of Si3N4 is enhanced significantly upon O2 injection into the NF3 discharge for O2/NF3 ratios of 0.3 and higher, whereas the SiO2 etch rate is less influenced for the same flow ratios. X-ray photoelectron spectroscopy of processed Si3N4 samples shows that the fluorine content of the reactive layer, which forms on the Si3N4 surface during etching, decreases with the flow of O2, and instead oxidation and nitrogen depletion of the surface occur. The oxidation of the reactive layer follows the same dependence on the flow of O2 as the etch rate. Argon actinometry and quadrupole mass spectrometry are used to identify rea- - ctive species in the etching of both materials. The atomic fluorine density decreases due to dilution as O2 is added to the discharge. The mass spectrometer did not detect NFx species (x=1–3) at any discharge parameter setting, which indicates the near complete dissociation of NF3. Nitric oxide (NO) was detected by mass spectrometry, and the NO density shows the same dependence on O2 flow as the Si3N4 etch rate and the surface oxidation. Based on this observation, we propose that the etch rate enhancement for Si3N4 is due to the adsorption of the NO on the Si3N4 surface, followed by the formation of N2 with a N atom from the surface. The O atom can then attach to the same surface site, contributing to the oxidation. © 1998 American Vacuum Society.   View full abstract»

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  • Effects of wall recombination on the etch rate and plasma composition of an etch reactor

    Page(s): 2057 - 2064
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    A helicon plasma etch reactor is simulated using direct simulation Monte Carlo and particle-in-cell methods for a chlorine (Cl2) feed gas flow. Computations for the gas discharge are carried out by modeling the ions and neutrals as particles and by imposing the electrons as a background condition conforming to experimental measurements. The neutrals and ions are then allowed to interact with the background electrons and to relax to a steady state. The effects on the reactor flow field and etch rate of chlorine atom recombination into chlorine molecules at the walls is investigated. Results show that recombination at the walls results in the depletion of the amount of chlorine atoms (Cl) in the reactor. The depleted chlorine atom population leads to lower ionization levels and a diminished ion (Cl+) flux to the wafer. Consequently, the etch rate is decreased by as much as 15% when compared to simulations without recombination. The creation of chlorine (Cl2) molecules at the walls through recombination also provides a new source for negative ions (Cl-) which increases the electronegativity of the plasma. In addition, the results of the simulation are compared with ion current and optical emission spectroscopy (OES) measurements. The Cl–Ar ratio (measured by the OES technique) increases less than 20% from the centerline to the wall of the reactor. An inspection of absolute densities, however, reveals that the individual near-wall densities are as much as a factor of 2 greater than the centerline densities. The trace species, Ar, therefore, does not become distributed evenly throughout the reactor. © 1998 American Vacuum Society. View full abstract»

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  • Radial distributions of ion velocity, temperature, and density in ultrahigh-frequency, inductively coupled, and electron cyclotron resonance plasmas

    Page(s): 2065 - 2072
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    Spatially resolved velocity distribution functions of metastable chlorine ions are measured in ultrahigh-frequency (UHF) plasma and compared with those in electron cyclotron resonance (ECR) plasma and inductively coupled plasma (ICP). In UHF plasma, ion velocity distribution function (IVDF) perpendicular to the surface normal of a wafer exhibits approximately no acceleration of ions to the side wall of a plasma reactor as the measuring point becomes radially far from the center of the reactor, even at 14 cm from the center where IVDF’s are shifted evidently in ECR plasma and ICP. This indicates that an almost flat profile of plasma potential is realized along the radius of the reactor in UHF plasma. As a consequence, metastable chlorine ion temperature remains low and almost constant over a radius of 14 cm in UHF plasma. Relative density of metastable chlorine ions in UHF plasma increases toward the side wall of the reactor. In contrast to this, the density exhibits a maximum in the center of the reactor and decreases towards the side wall in ECR plasma and ICP. The increased densities near the side wall in UHF plasma imply increased plasma production off the symmetry axis of the reactor, which makes UHF plasma uniform in a wider region than in ECR plasma and ICP. The effect of the discharge frequency on radial distribution of metastable chlorine ion density is also discussed. © 1998 American Vacuum Society.   View full abstract»

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  • Reactive sputtered titanium carbide/nitride and diamondlike carbon coatings

    Page(s): 2073 - 2077
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    Nitride and carbide coatings of titanium and diamondlike carbon (DLC) coatings containing a small amount of titanium were deposited onto AISI 420 substrates by unbalanced magnetron sputtering techniques. The structures of the different coatings were analyzed by x-ray diffraction, Rutherford backscattering spectrometry, and infrared spectroscopy. The TiN, TiCxNy, and TiC coatings exhibited strong (111), (111), or (200) and (220) preferential orientations, respectively. The different tribological behaviors of TiN, TiC, TiCxNy, and DLC coatings were investigated and compared. In addition, the microhardness and adhesion of the coatings were also measured. The hardness values for all the coatings increased with the carbon content going from pure TiN to the DLC coating. The experimental results indicated that the DLC-10%Ti coating showed excellent properties, i.e., a high microhardness value (about 40.0 GPa), excellent adhesion (about Lc 11.0 kg), a lower friction coefficient, and an extremely long wear lifetime (about 58 h). © 1998 American Vacuum Society. View full abstract»

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  • Influence of surface impurities on plasma-driven permeation of deuterium through nickel

    Page(s): 2078 - 2083
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    The plasma-driven permeation behavior of deuterium through nickel membrane was examined in the temperature range from room temperature to 723 K. The modification of its surface impurities by exposing it to the hydrogen plasma was examined with Auger electron spectroscopy. The influence of surface impurities on the penetration and recombination behavior of deuterium atoms at the nickel surface is discussed. © 1998 American Vacuum Society. View full abstract»

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  • Properties of various sputter-deposited Cu–N thin films

    Page(s): 2084 - 2092
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    Compositions and structures of sputter-deposited Cu–N films are strongly dependent on the total sputtering pressure and on the content of nitrogen gas. The Cu–N films obtained can be classified into four categories: metallic Cu-rich Cu3N films with a positive temperature coefficient of resistivity (TCR), semiconducting Cu-rich Cu3N films, semiconducting stoichiometric Cu3N films, and semiconducting N-rich Cu3N films with a negative TCR. The current–voltage curves of various Cu–N films are presented. The metallic conduction and semiconductor conduction are two main electrical conduction mechanisms for various Cu–N films. The decomposition temperature of various Cu–N films has been determined to be around 604–614 K using both thermogravimetry and dynamical measurement of electrical resistance during heating in a vacuum furnace. The great scattering of data over the electrical resistivity of Cu3N reported up to now is mainly due to the nonstoichiometry of the Cu3N. The optical band gap of stoichiometric Cu3N is determined to be around 1.8–1.9 eV, but it decreases with the decrease in the degree of stoichiometry. © 1998 American Vacuum Society. View full abstract»

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  • Carbon nitride thin-film growth by pulsed laser deposition

    Page(s): 2093 - 2098
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    Thin films of carbon nitride were deposited using pulsed laser deposition techniques both with and without an atomic nitrogen source. In situ characterization of chemical composition and atomic bonding were studied using scanning Auger, x-ray photoelectron spectroscopy, and electron energy-loss spectroscopy. The influence of growth parameters including substrate temperature, substrate bias, nitrogen partial pressure, and atomic nitrogen on the film composition were studied. Nitrogen content x for CNx films ranged from 0.3 to 0.6 (25–40 at. % nitrogen). Time-of-flight mass spectrometry of the species ejecting from a nitrided carbon target was performed. Neutrals of CN4 and C3N4 clusters and positive ions of CxNy clusters were observed in addition to carbon neutral and positive ion clusters. © 1998 American Vacuum Society. View full abstract»

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  • Influence of reactor wall conditions on etch processes in inductively coupled fluorocarbon plasmas

    Page(s): 2099 - 2107
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    The influence of reactor wall conditions on the characteristics of high density fluorocarbon plasma etch processes has been studied. Results obtained during the etching of oxide, nitride, and silicon in an inductively coupled plasma source fed with various feedgases, such as CHF3, C3F6, and C3F6/H2, indicate that the reactor wall temperature is an important parameter in the etch process. Adequate temperature control can increase oxide etch selectivity over nitride and silicon. The loss of fluorocarbon species from the plasma to the walls is reduced as the wall temperature increased. The fluorocarbon deposition on a cooled substrate surface increases concomitantly, resulting in a more efficient suppression of silicon and nitride etch rates, whereas oxide etch rates remain nearly constant. © 1998 American Vacuum Society. View full abstract»

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  • Electrical impedance analysis and etch rate maximization in NF3/Ar discharges

    Page(s): 2108 - 2114
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    We have investigated the etching of SiO2 and plasma chemically vapor deposited (CVD) SiNxHy (SiN) thin films in NF3/Ar plasmas as a function of pressure, NF3 concentration in Ar, and rf power. We have also independently measured the complex impedance and real power dissipation of the discharges. By simultaneously varying the pressure and NF3 concentration we have determined that the highest etch rates are obtained at low concentrations of NF3 in Ar (18%–25%) for both SiO2 and SiN at relatively high pressure (1550 mTorr). Etch rates of 14 800 Å/min for SiN and 1600 Å/min for SiO2 are achieved under these conditions. The SiN etch rate is found to be a strong function of the applied rf power, which also determines the pressure at which the highest etch rates are achieved. Both the SiN and SiO2 etch rates were found to be closely correlated to the argon and fluorine atom optical emission intensities. For NF3 partial pressures above 200 mTorr the NF3/Ar plasmas had very high impedance magnitudes (≫5000 Ω) and low power coupling efficiencies (≪25%). These results indicate that there is an optimal NF3 partial pressure for obtaining high etch rates which supp- - lies sufficient reactant, but is low enough to maintain a low impedance and high power coupling efficiency. To explain these results we propose that the role of argon in NF3 based plasmas under these conditions is to lower the electronegativity of the discharge through dilution and/or reactions in the discharge. The results of this study provide insight into the optimization of processes which use fluorinated gases in plasmas at high pressures such as plasma enhanced CVD chamber cleaning where fast removal of silicon based materials is required. © 1998 American Vacuum Society. View full abstract»

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  • Chemical downstream etching of tungsten

    Page(s): 2115 - 2119
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    The downstream etching of tungsten and tungsten oxide has been investigated. Etching of chemical vapor deposited tungsten and e-beam deposited tungsten oxide samples was performed using atomic fluorine generated by a microwave discharge of argon and NF3. Etching was found to be highly activated with activation energies approximated to be 6.0±0.5 kcal/mol and 5.4±0.4 kcal/mol for W and WO3 , respectively. In the case of F etching of tungsten, the addition of undischarged nitric oxide (NO) directly into the reaction chamber results in the competing effects of catalytic etch rate enhancement and the formation of a nearly stoichiometric WO3 passivating tungsten oxide film, which ultimately stops the etching process. For F etching of tungsten oxide, the introduction of downstream NO reduces the etch rate. © 1998 American Vacuum Society. View full abstract»

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  • Electrical and optical properties of amorphous fluorocarbon films prepared by plasma polymerization of perfluoro-1,3-dimethylcyclohexane

    Page(s): 2120 - 2124
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    The electrical and optical properties of amorphous fluorocarbon films (a-C:F) prepared by plasma polymerization have been investigated. Perfluoro-1,3-dimethylcyclohexane was introduced into a parallel plate plasma reactor operating at 13.56 MHz to deposit a-C:F films. Transparent a-C:F films with an F/C ratio of 2 were prepared at lower power densities of 10–300 mW/cm2 at deposition rates of 4–10 nm/min. The films have a low surface energy of 15 mN/m and are thermally stable up to 210 °C. The coatings exhibit low refractive index of 1.38, low dielectric constant of 2.3, and high transmittance in the visible range. The electret properties were evaluated by measuring the decay of a positive surface potential (SPD) on 25 μm thick a-C:F films. High rf power densities lead to an increased formation of conjugated C–C double bonds affecting the transmittance and SPD characteristic. However, the relative low thermal stability, insufficient planarization, and charge storage capabilities limit the applications of the a-C:F films for microelectronic and electrical applications. © 1998 American Vacuum Society. View full abstract»

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  • Metal bonding during sputter film deposition

    Page(s): 2125 - 2131
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    We studied the bonding between two flat Si substrates with thin metal films. The bonding was accomplished during thin film sputter deposition on contamination free surfaces of metal films. In this work we used Ti and Pt. Successful bonding of these metal films (each having a thickness of 10–20 nm) occurred at room temperature over the entire bonded area (12 mm×12 mm). Self-diffusion, particularly at grain boundaries and film surface, was the mechanism for bonding. Suitable metal bonding only occurred if the film surface roughness is sufficiently smaller than the self-diffusion length of metals. Particularly in the bonding of Ti to Ti films, transmission electron microscope observation revealed that complete crystalline grains had been formed across the former interface between the single thin Ti films. The interfaceless bonding can be explained by recrystallization of the Ti lattice due to the high self-diffusion coefficient of Ti. This technique would be applied to bonding of wafers to fabricate thin film devices or microsystems. Moreover, this bonding technology can be used with many different thin film materials and various semiconductor substrates. © 1998 American Vacuum Society. View full abstract»

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  • Kinetic energy distribution of nitrogen ions in an electron cyclotron resonance plasma

    Page(s): 2132 - 2139
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    In this article, the kinetic energy distribution of atomic and molecular nitrogen ions is reported for two electron cyclotron resonance (ECR) sources. Methods to reproducibly tune the kinetic energy of ionic species from 3 eV to 35 eV have been developed in order to produce monoenergetic ion beams for the demanding requirements of selective energy epitaxy. This article also describes methods to avoid the discontinuous hysteretic transitions between stable ECR modes. The changes in the ion energy distribution resulting from these abrupt transitions are characterized. © 1998 American Vacuum Society. View full abstract»

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  • Molecular beam epitaxial growth of AlN single crystalline films on Si (111) using radio-frequency plasma assisted nitrogen radical source

    Page(s): 2140 - 2147
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    We have grown AlN films on Si (111) using a molecular beam epitaxy (MBE) approach in which reactive nitrogen species are generated in a remote 13.56 MHz radio-frequency plasma discharge, nitrogen radical source. Effects of the Al/Si (111) γ-phase on epitaxial growth of AlN on Si (111) has been studied. Successive processes of forming stable Al/Si (111) γ-phase at 800 °C followed by MBE growth without interrupting Al beam exposure was effective to prevent amorphous SiNx formation on Si substrate. The Al/Si (111) γ-phase was found effective to fix the orientation relationship between AlN and Si for epitaxial growth of single crystal AlN. Single crystal AlN was grown on the Al/Si (111) γ-phase at the temperature as low as 400 °C. By optimizing growth conditions (substrate temperature, V/III ratio and plasma conditions), growth of single crystal AlN films in a quasi-layer-by-layer fashion was observed for the thickness up to 60 nm. The optimized value on the growth temperature was 800 °C and that on the V/III ratio was 440. The surface of the AlN film grown under the optimized condition was quite smooth with a root mean square roughness of 0.3 nm. The resistivity of the film was about 2×109 Ω cm. © 1998 American Vacuum Society. View full abstract»

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  • Distribution of species within an ethylene electron cyclotron resonance-microwave plasma

    Page(s): 2148 - 2152
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    Electron cyclotron resonance microwave plasmas consisting of 2% ethylene in hydrogen and 2% ethylene in deuterium have been probed using the pulsed supersonic, plasma sampling technique. Comparison of the compositions of these two chemically equivalent plasmas provides the basis for examining the details of species interconversion and overall hydrocarbon chemistry within these plasmas. The ethylene/hydrogen plasma is shown to be composed of 9% ethane radical (C2H5), 38% ethylene (C2H4), 8% ethylene radical (C2H3), and 41% acetylene (C2H2), with the remaining counts attributed to impurities in the plasma. Due to interferences between the daughter ions of the radical species and the parent ions of ethylene and acetylene, the concentrations of radical species, reported above, represent only a lower limit estimate, based only on the parent ion intensity. Analysis of the mass spectrum obtained for the analogous deuterium plasma, based on the results from the hydrogen plasma experiments, reveal the acetylene components of the deuterium plasma to be 14% undeuterated (C2H2), 43% singly deuterated (C2HD), and 43% doubly deuterated (C2D2). The extensive deuteration of the acetylene indicates that the majority of the chemistry in these plasmas is repeated cycles of hydrogen (deuterium) atom addition to acetyl- - ene followed by abstractions from the radical species (C2HxD3-x). The absence of any significant intensity due to doubly, triply, or fully deuterated ethylenes indicates that the addition of hydrogen (deuterium) to the radical species C2HxD3-x is a much more rare event than abstraction. © 1998 American Vacuum Society. View full abstract»

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  • Inductively coupled plasma etch processes for NiMnSb

    Page(s): 2153 - 2161
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    Plasma chemistries based on SF6, NF3, or CH4/H2 were investigated for inductively coupled plasma (ICP) etching of NiMnSb Heusler alloy thin films. The resulting etch rates were a strong function of ion energy, ion flux, and plasma composition. In SF6/Ar discharges, the etch rates increased from 100 to 300 Å min-1 under conventional reactive ion etch conditions to ≫10 000 Å min-1 with the addition of even relatively small amounts (200 W) of ICP source power. The etched surface becomes enriched in Mn under these conditions. In NF3/Ar discharges the etch rates actually decrease as ICP source power is increased, leading to net deposition at either high NF3 percentages or high ICP powers. The etched surface is also enriched in Mn under these conditions, with a Sb-deficient region underneath. In CH4/H2/Ar discharges, the etch rates are slower than with pure Ar and show no evidence of a chemical component in the etch mechanism. Since the etch rates are so high in ICP SF6/Ar discharges, it is necessary to pay careful attention to removal of the native oxide on NiMnSb, which prevents etching while it is present, and thus may cause extremely rough surfaces if it not uniformly removed.© 1998 American Vacuum Society.   View full abstract»

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  • Dually driven radio frequency plasma simulation with a three moment model

    Page(s): 2162 - 2172
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    This article presents simulation results of a dually excited capacitive rf plasma reactor. A self-consistent three moment model is employed which is shown to accurately capture the ion flux and energy at the substrate. Self-dc biases at the powered electrodes are also self-consistently determined by relating surface charges through Gauss’ law. The simulation results of this rf triode system indicate that plasma density is predominantly determined by the primary electrode. Self-bias and ion bombardment energy at the secondary electrode both exhibit linear (logarithmic) dependency on the secondary rf power (frequency). This is qualitatively in good agreement with experimental results. © 1998 American Vacuum Society. View full abstract»

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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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G. Lucovsky
North Carolina State University