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

Issue 5 • Date Sep 2008

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Displaying Results 1 - 25 of 44
  • Issue Cover

    Page(s): c1
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  • Issue Table of Contents

    Page(s): toc1
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  • Magnetron sputtered Si–B–C–N films with high oxidation resistance and thermal stability in air at temperatures above 1500 °C

    Page(s): 1101 - 1108
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    Novel quaternary Si–B–C–N materials are becoming increasingly attractive because of their possible high-temperature and harsh-environment applications. In the present work, amorphous Si–B–C–N films were deposited on Si and SiC substrates by reactive dc magnetron cosputtering using a single C–Si–B or B4CSi target in nitrogen-argon gas mixtures. A fixed 75% Si fraction in the target erosion areas, a rf induced negative substrate bias voltage of -100 V, a substrate temperature of 350 °C, and a total pressure of 0.5 Pa were used in the depositions. The corresponding discharge and deposition characteristics (such as the ion-to-film-forming particle flux ratio, ion energy per deposited atom, and deposition rate) are presented to understand complex relationships between process parameters and film characteristics. Films deposited under optimized conditions (B4CSi target, 50% N2+50% Ar gas mixture), possessing a composition (in at. %) Si32–34B9–10C2–4N49–51 with a low (less than 5 at. %) total content of hydrogen and oxygen, exhibited extremely high oxidation resistance in air at elevated temperatures (even above 1500 °C). Formation of protective surface layers (mainly composed of Si and O) was proved by high-resolution transmission electron microscopy, Rutherford backscattering spectrometry, a- - nd x-ray diffraction measurements after oxidization. Amorphous structure of the Si–B–C–N films was maintained under the oxidized surface layers after annealing in air up to 1700 °C (a limit imposed by thermogravimetric analysis in oxidative atmospheres). View full abstract»

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  • Investigation of the suppression effect of polyethylene glycol on copper electroplating by electrochemical impedance spectroscopy

    Page(s): 1109 - 1114
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    Polyethylene glycol (PEG) is an additive that is commonly used as a suppressor in the semiconductor copper (Cu)-electroplating process. In this study, electrochemical impedance spectroscopy (EIS) was used to analyze the electrochemical behavior of PEG in the Cu-electroplating process. Polarization analysis, cyclic-voltammetry stripping, and cell voltage versus plating time were examined to clarify the suppression behavior of PEG. The equivalent circuit simulated from the EIS data shows that PEG inhibited the Cu-electroplating rate by increasing the charge-transfer resistance as well as the resistance of the adsorption layer. The presence of a large inductance demonstrated the strong adsorption of cuprous-PEG-chloride complexes on the Cu surface during the Cu-electroplating process. Increasing the PEG concentration appears to increase the resistances of charge transfer, the adsorption layer, and the inductance of the electroplating system. View full abstract»

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  • Silane injection in a high-density low-pressure plasma system and its influence on the deposition kinetics and material properties of SiO2

    Page(s): 1115 - 1119
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    High-rate, low temperature deposition is an essential requirement for industrial fabrication technology to be suitable for the deposition of optical and protective coatings. High-density, low-pressure plasmas have received significant attention for such applications due to their ability to create large and controllable ion fluxes onto the substrate. In this study, the high-rate deposition of silica films from a silane and oxygen gas mixture in a high-density plasma system based on a matrix distributed electron cyclotron resonance (MDECR) plasma source is investigated using directional jet injection of undiluted silane. The influence of process parameters such as the microwave power, radio frequency biasing of the substrate holder, and gas flows on the OH content of the oxide films is studied using phase-modulated spectroscopic ellipsometry (SE), Fourier transform infrared (FTIR) spectroscopy, and transmission measurements. The results of the measurements, taken at various points across the wafer, show a decrease in the thickness-normalized OH concentration in the areas of higher deposition rates. The corresponding gas phase composition is investigated using optical emission spectroscopy and compared to the FTIR, transmission and SE measurement results in order to validate our findings and ultimately optimize the deposition process. It is found that the primary silane flux onto the surface, which depends on the positioning of the jet injection point and gas flow rate, plays an important role not only on the deposition rate but also on the OH content of the films. The authors conclude that high-density plasma deposition systems such as the MDECR plasma enhanced chemical vapor deposition system cannot be considered as well mixed for gases with dissociation products that have high sticking coefficients, contrary to the accepted paradigm. View full abstract»

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  • Low energy secondary ion mass spectrometry with sub-keV O2+ beams at glancing incidence

    Page(s): 1120 - 1127
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    The ever increasing interest in surface analysis techniques with excellent depth resolution, great detection sensitivity, and good throughput has been a driving force for development of dynamic secondary ion mass spectrometry using low energy primary beams. This work investigated sputtering erosion of Si and emission of secondary ions from Si bombarded by sub-keV O2+ beams at glancing incidence. It was demonstrated that surface roughening remained minimal for 250 and 500 eV O2+ beams at an angle of incidence above 80° but developed rapidly at angles between 60° and 80°. The depth resolution for B and Ge appeared very different at the glancing incidence and changed dramatically in opposite ways as the angle of incidence decreased. The difference in the depth resolution was explained by the different diffusion/segregation behavior between B and Ge during O2+ bombardment. In general, the use of sub-keV O2+ beams at the glancing incidence (above 80°) favored a thinner altered layer, a short surface transient, a minimal apparent shift in depth profiles, a better depth resolution (not for B in Si), a good sputter rate, but a poor yield of the positive secondary ions. To address the issues with the low ion yield, we identified optimal cluster ions for common dopant such as boron and nitrogen. Good sensitivity was achieved for analyses of boron in Si by detecting BO2- as the characteristic secondary ion. A parallel study published elsewhere suggested SiN- as an ideal candi- - date for detection of nitrogen in ultrathin oxynitride [Z. X. Jiang etal, Surf. Interface Anal. (in press)]. For analyses of thin SiGe films in Si at glancing incidence, detection of Ge+ provided fairly good sensitivity. Applications of an O2+ beam at 250 eV 83° for analyses of shallow boron implant demonstrated superior accuracy in the measured near-surface boron distribution. Also the characterization of thin SiGe films exhibited excellent depth resolving power for Ge in Si although the ion yield of Ge+ was low. View full abstract»

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  • Measurement of reactive and condensable gas permeation using a mass spectrometer

    Page(s): 1128 - 1137
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    Permeation of water vapor, oxygen, nitrogen, and carbon dioxide through polymer films is measured by the programed valving mass spectrometry (PVMS) method. The results are calibrated with a standard permeation rate for each gas to determine the detection sensitivity. The calibrated lower detection limits are 1.90×10-7 g/m2 day for water vapor, 2.81×10-2 cm3/m2 day for oxygen, 2.15×10-2 cm3/m2 day for nitrogen, and 3.29×10-2 cm3/m2 day for carbon dioxide. The lower detection limits presented here for water vapor, nitrogen, and carbon dioxide are more than two orders of magnitude lower than the corresponding values offered by the NIST-traceable standard techniques. In addition, the PVMS water vapor lower detection limit meets the sensitivity requirement for detecting “ultrabarrier” water vapor permeation rates, while the oxygen lower detection limit is higher than that offered by the standard technique. However, the results suggest a modified measurement protocol and/or system modifications to overcome this limitation. Effusivity through a flow orifice was also examined using the PVMS method for the above gases. The effusion results from the flow orifice, combined with the permeation results from polymer samples, provide insight into the factors that may influence gas detection sensitivities. View full abstract»

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  • Identification and quantification of iron silicide phases in thin films

    Page(s): 1138 - 1148
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    Iron silicide samples were grown on Si (111) substrates by solid phase epitaxy and reactive deposition epitaxy. The different iron silicide phases and their correlations with the growth parameters were analyzed by x-ray photoelectron spectroscopy, conversion electron Mössbauer spectroscopy, x-ray diffraction, atomic force microscopy, and magnetic force microscopy. The authors investigated the potential of each technique for identifying and quantifying of the phases. In particular, the authors used a semiquantitative analysis of magnetic force microscopy images to spatially resolve the semiconductor β-FeSi2 phase. View full abstract»

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  • Structure and mechanical properties of diamondlike carbon films produced by hollow-cathode plasma deposition

    Page(s): 1149 - 1153
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    Diamondlike carbon (DLC) films are deposited on AISI 304 stainless-steel substrates using hollow-cathode chemical vapor deposition. The effects of the substrate bias on the structural and mechanical properties of the films are studied. X-ray photoelectron spectroscopy reveals the existence of CC (sp2) and C–C (sp3) functional groups in the films, and Raman spectra show that the ratio of the G (graphite) peak to the D (disorder) peak depends on the sample bias. The DLC film deposited at -50 V bias has the highest sp3 content, and this is consistent with the G-band position and D-band full width at half maximum as a result of substrate biasing. The sample bias also has a critical influence on the thickness and hardness of the deposited films. The largest thickness (1700 nm) and highest hardness (HV1099) are achieved at a bias voltage of -50 V. All the films show low friction coefficients, and the sample treated at -200 V gives rise to the lowest friction coefficient. View full abstract»

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  • Wafer heating mechanisms in a molecular gas, inductively coupled plasma: in situ, real time wafer surface measurements and three-dimensional thermal modeling

    Page(s): 1154 - 1160
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    The authors report measurements and modeling of wafer heating mechanisms in an Ar/O2 inductively coupled plasma (ICP). The authors employed a commercially available on-wafer sensor system (PlasmaTemp™ developed by KLA-Tencor) consisting of an on-board electronics module housing battery power and data storage with 30 temperature sensors embedded onto the wafer at different radial positions. This system allows for real time, in situ wafer temperature measurements. Wafer heating mechanisms were investigated by combining temperature measurements from the PlasmaTemp™ sensor wafer with a three-dimensional heat transfer model of the wafer and a model of the ICP. Comparisons between pure Ar and Ar/O2 discharges demonstrated that two additional wafer heating mechanisms can be important in molecular gas plasmas compared to atomic gas discharges. The two mechanisms are heating from the gas phase and O-atom surface recombination. These mechanisms were shown to contribute as much as 60% to wafer heating under conditions of low bias power. This study demonstrated how the “on-wafer” temperature sensor not only yields a temperature profile distribution across the wafer, but can be used to help determine plasma characteristics, such as ion flux profiles or plasma processing temperatures. View full abstract»

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  • Capillary flow meter for calibrating spinning rotor gauges

    Page(s): 1161 - 1165
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    This article describes a capillary flow meter whose maximum flow rate of 0.2 μmol/s (∼0.2 cm3/min at ambient conditions) covers the range that is useful for calibrating spinning rotor gauges. Knowing the input pressure, output pressure, and temperature of the capillary yields the gas flow rate with a relative standard uncertainty as small as 0.04%. The flow meter, which requires no moving parts aside from valves, comprises a ballast tank, a coil of quartz capillary with an inner diameter of 0.1 mm, and a commercial instrumentation package. Measurements near 0.1 μmol/s showed agreement with an independent primary flow meter to within 0.2%, comparable to the combined relative standard uncertainty of 0.11%. Additional measurements showed that operating the capillary flow meter with an exit pressure less than 1 kPa allowed the flow to stabilize within minutes. However, the small exit pressure caused an unexpected enhancement of the slip correction in the hydrodynamic model of the capillary. View full abstract»

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  • Reduction in hydrogen outgassing from stainless steels by a medium-temperature heat treatment

    Page(s): 1166 - 1171
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    The authors carried out heat treatments, in-vacuum or in-air at 400 °C, to reduce the hydrogen outgassing rate from stainless steels. An outgassing rate as low as 2×10-14 Torr ℓ s-1cm-2 was routinely achieved by a medium-temperature bakeout, but it took much longer time than reported to perform intensive thermal treatment. The result shows that the diffusion process governs degassing only at the early stage of degassing while the recombination limits outgassing at low concentrations. Air baked chambers had somewhat lower outgassing rates than in-vacuum baked chambers, suggesting that the surface oxide acts as a further barrier for H2 outgassing. However, the main effect may be attributed to the removal of mobile hydrogen through diffusion. The results showed that the ultralow outgassing rate can be reproducibly achieved for stainless steel chambers with the established heat treatment procedure. The study also showed that the ultralow outgassing property of a treated chamber can be restored by a low temperature (≫150 °C) postbakeout, after exposure to ambient air. View full abstract»

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  • Trench profile angle beveling

    Page(s): 1172 - 1177
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    A trench bevel etch process is developed as a method to produce trench profiles with a prerequired angle. This process depends on both surface reaction and gas conductance along the trench. To study the surface reaction probability, activation energies were measured for SF6 and CF4 chemistries and were found to be 6 and 140 meV, respectively. It has been demonstrated that CF4 etch chemistry is in surface-reaction-rate-limited regime and contributes little to the trench beveling. SF6 chemistry with its low activation energy is in reactant-transport-rate-limited regime and contributes significantly to the bevel process. The dependences of bevel etch on trench aspect ratio was also investigated in detail. It has been found that high aspect ratio trench produces larger bevel angle than that does for small aspect ratio. A phenomenological model was constructed by introducing reactant conduction loss L and sidewall reaction loss S to quantitatively describe the effects of both reactant transport and surface reaction. Through comparison of theoretical modeling and experiment, an S value between 0.8 and 1 is reached to explain the experimental results from SF6 chemistry. This result demonstrates the SF6 is a spontaneous surface reaction and is consistent with our activation energy measurement. View full abstract»

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  • Ferroelectric properties of Bi3.25La0.75Ti3O12 films using HfO2 as buffer layers for nonvolatile-memory field-effect transistors

    Page(s): 1178 - 1181
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    The ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin film and HfO2 layer were fabricated using both metal-organic decomposition and atomic-layer deposition methods. The HfO2 thin film was deposited as a buffer layer between Si substrate and BLT thin films. The electrical and structural properties of the metal-ferroelectric-insulator-semiconductor (MFIS) structure were investigated by varying the HfO2 layer thickness. Transmission electron microscopy showed no interdiffusion and reaction occurring when the HfO2 film is used as a buffer layer. The width of the memory window in the capacitance-voltage curves for the MFIS structure was decreased with increasing thickness of the HfO2 buffer layer. The experimental results showed that the BLT-based MFIS structure is suitable for nonvolatile-memory field-effect transistors with a large memory window. View full abstract»

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  • Cyclic, cryogenic, highly anisotropic plasma etching of silicon using SF6/O2

    Page(s): 1182 - 1187
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    The authors report on the development and characterization of a plasma etching method that utilizes process steps common to both the well-known Bosch and the cryogenic deep reactive ion etching methods for silicon. This hybrid process uses cyclical etch steps that alternate between etching and passivating chemistries as in the Bosch process, while still maintaining sample temperatures at -100 °C on a cryogenically cooled stage. The advantages of this process are superior control of wall profiles for isolated features, minimization of grass formation, and the elimination of an expensive gas, c-C4F8, required in the Bosch passivation step. The authors show examples of x-ray optic elements deep etched to 100 μm depth with the cyclic cryogenic process. View full abstract»

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  • Influence of N2 gas pressure and negative bias voltage on the microstructure and properties of Cr–Si–N films by a hybrid coating system

    Page(s): 1188 - 1194
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    Cr–Si–N films were deposited using a hybrid coating system combining arc ion plating and magnetron sputtering. The authors investigated the influence of N2 flux rate and negative bias voltage on the microstructure and properties of Cr–Si–N films, e.g., chemical composition, film morphology, phase structure, residual stress, and microhardness. The results showed that all the Cr–Si–N films were close to stoichiometry. The N2 flux rate had no important influence on the microstructure and properties of the Cr–Si–N films. Applying a negative bias voltage resulted in significant decrease in macroparticle densities and smoother film surface. Also the film microstructure transformed from apparent columnar to nanocomposite microstructure. The maximum microhardness obtained ranged from 45 to 50 GPa at a bias voltage ranging from -50 to -100 V. The microhardness enhancement could be ascribed to the mixed effect of grain size diminishment and residual compressive stress. View full abstract»

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  • Enhanced chemical immunity for negative electron affinity GaAs photoemitters

    Page(s): 1195 - 1197
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    Negative electron affinity GaAs photoemitters require ultrahigh vacuum conditions to achieve the best performance and to maintain the quantum yield. This limits their utility in applications where the background pressure is high. The authors have developed an activation procedure by which the reactivity to CO2, a principal cause of yield decay, is greatly reduced. The use of a second alkali in the activation process is responsible for the increased immunity of the activated surface. The best immunity was obtained by using a combination of Cs and Li without any loss in near band gap yield. View full abstract»

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  • Study of fluorocarbon plasma in 60 and 100 MHz capacitively coupled discharges using mass spectrometry

    Page(s): 1198 - 1207
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    The signals of positive ions and radicals formed in the fluorocarbon plasma of the capacitively coupled plasma reactor were measured using a quadrupole mass spectrometry and optical emission actinometry. The plasma was produced at 60 and 100 MHz frequencies for the same reactor configuration and gas mixtures. Experiments were performed at 25 mTorr with a SiO2 wafer on the grounded electrode. Mass spectra of ions were measured in C4F8/O2/Ar and C4F6/O2/Ar gas mixtures at 500–1500 W generator powers. For 60 and 100 MHz discharges production of fluorocarbon ions and radicals is discussed. It was found that the production of heavy species increases with frequency. The high mass signals such as C3F3+, C2F4+, C2F5+, C3F5+, C4F7+ decrease when CHF3 is added to the gas mixture. However, the signals of CFx+ (x=1,2,3) do not change significantly. These re- - sults are compared to the results of polymer film deposition on the wafer. It was suggested to control the polymerization film formation by adding small amount of CHF3 to the process mixture. View full abstract»

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  • On the phase identification of dc magnetron sputtered Pt–Ru alloy thin films

    Page(s): 1208 - 1212
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    The microstructure and the electronic work function of Pt–Ru alloy thin films spanning the compositional range from pure Pt to pure Ru were investigated. Nominally 50 nm thick films were cosputtered from elemental targets in an ultrahigh vacuum chamber. X-ray reflectivity and Rutherford backscattering spectroscopy were used to determine the film thicknesses and compositions. The electronic work function of the alloy film samples was determined by analysis of the capacitance-voltage characteristics of films deposited as part of a metal-oxide-semiconductor capacitor structure and found to range from 4.8 eV for pure Ru to 5.2 eV for pure Pt. To better understand the variation in work function for the intermediate compositions, the films were characterized by transmission electron microscopy and x-ray and electron diffractions. A notable increase in the compositional range of the hexagonal close packed (hcp) phase was observed, suggesting a metastable extension of the hcp phase stability as compared to bulk Pt–Ru alloys. The steepest change in the electronic work function for the intermediate alloy compositions coincided with a rapid change in the c/a ratio of the hcp phase. View full abstract»

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  • Enhancement of metal oxide deposition rate and quality using pulsed plasma-enhanced chemical vapor deposition at low frequency

    Page(s): 1213 - 1217
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    The deposition rate and quality of alumina thin films fabricated by plasma-enhanced chemical vapor deposition (PECVD) increased significantly when square wave power modulation was applied at low frequency (∼1 Hz). The pulsed PECVD rate was enhanced by a factor of ∼3 relative to continuous wave operation, and the quantity of impurities was dramatically attenuated. Deposition experiments on trenches with aspect ratios ranging from 4 to infinity demonstrated that the technique achieves a high degree of conformality. Important reactor design and operating considerations are described. Pulsed PECVD produced similar quality improvements for Ta2O5, TiO2, and ZnO, suggesting that the approach has widespread potential for metal oxide synthesis. View full abstract»

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  • Origin of hydrogen desorption during friction of stainless steel by alumina in ultrahigh vacuum

    Page(s): 1218 - 1223
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    A study of the tribodesorption of hydrogen stimulated by the friction of an alumina pin on stainless steel in ultrahigh vacuum at room temperature is presented. A special two-chamber ultrahigh-vacuum system separated by a well-defined orifice of low conductance is used to determine minute amounts of desorbed gases. The friction cell allows the control of the normal force of the alumina pin on the stainless-steel surface, the frequency of sweeping, as well as the dwell, i.e., the time between consecutive strokes. The profile of the p(H2)-t desorption curve shows a near-exponential increase in pressure to a stable value; then, after the friction cessation, the pressure decreases back to the initial value. The desorption curve presents an oscillating signal over the continuous one that corresponds with the sweeping frequency. An important aspect of the present research has been to elucidate the origin of the desorbed hydrogen: bulk or surface of materials. In this respect, the amount of tribodesorbed hydrogen is compared with the amount of adsorbed hydrogen at dwell times from 0.5 to 4 s. This adsorption is 50 and 5 times lower than the desorbed hydrogen at normal forces of 0.072 and 0.218 N, respectively, and a dwell time of 4 s. An important finding is that the amount of desorbed hydrogen is irrespective of the dwell time, and the desorption rate increases linearly with sweeping frequency. The authors conclude that the origin of the desorbed hydrogen is in the bulk. View full abstract»

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  • Two-silane chemical vapor deposition treatment of polymer (nylon) and oxide surfaces that yields hydrophobic (and superhydrophobic), abrasion-resistant thin films

    Page(s): 1224 - 1234
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    This article describes a two-silane, chemical vapor deposition (CVD) approach to creating hydrophobic (or even superhydrophobic), abrasion-resistant coatings on silicon oxide and polymer (nylon) substrates. This multistep approach employs only reagents delivered in the gas phase, as follows: (i) plasma cleaning/oxidation of the substrate, (ii) CVD of 3-isocyanatopropyltriethoxysilane, which is used as an adhesion promoter for the substrate, (iii) hydrolysis with water vapor, and (iv) CVD of (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane (the “Rf-Cl silane”). Surfaces are characterized by wetting, spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). This work has the following unique features. First, the authors explore an all gas phase deposition of a new silane coating that is scientifically interesting and technologically useful. Second, the authors show that the presence of an adhesion promoter in the process leads to thinner films that are more robust in abrasion testing. Third, results obtained using plasma/deposition equipment that is relatively inexpensive and/or available in most laboratories are compared to those obtained with a much more sophisticated, commercially available plasma/CVD system (the YES-1224P). The entire deposition process can be completed in only ∼1 h using the industrial equipment (the 1224P). It is of significance that the polymer surfaces modified using the 1224P are superhydrophobic. Fourth, the thickness of the Rf-Cl silane layer deposited by CVD correlates well with the thickness of the underlying spin coated nylon surface, suggesting that the nylon film acts as a reservoir of water for the hydrolysis and condensation of the Rf-Cl silane. View full abstract»

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  • Growth and interface of HfO2 films on H-terminated Si from a TDMAH and H2O atomic layer deposition process

    Page(s): 1235 - 1240
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    HfO2 thin films have been deposited by an atomic layer deposition (ALD) process using alternating pulses of tetrakis(dimethyl)amino hafnium and H2O precursors at a substrate temperature of 200–325 °C. The initial stage of film growth on OH- and H-terminated Si(100) surfaces is investigated using Rutherford backscattering spectrometry (RBS), x-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The authors observe an initial growth barrier on the Si–H surface for the first approximately four process cycles, where film growth is more efficient on the OH-terminated surface. Both starting surfaces require about 15 cycles to reach a steady growth rate per cycle, with the OH-terminated surface displaying a slightly higher growth rate of 2.7×1014 Hf/cm2 compared to 2.4×1014 Hf/cm2 for Si–H. Combining the RBS and SE data we conclude that the films deposited on the OH-terminated surface are denser than those deposited on the Si–H surface. Angle-resolved XPS measurements reveal the formation of an ∼8 Å interfacial layer after four ALD cycles on the H-terminated surface for a deposition temperature of 250 °C, and transmission electron microscopy verifies that the thickness of the interfacial layer does not change substantially between the 4th and the 25th process cycles. The interfacial layer appears to depend weakly on the deposition temperature from 200 to 325 °C, rang- - ing from 6.9 to 8.4 Å. View full abstract»

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  • Unique lack of chemical reactivity for 2,3-dimethyl-2-butene on a Si(100)-2×1 surface

    Page(s): 1241 - 1247
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    Adsorption of 2,3-dimethyl-2-butene on Si(100)-2×1 has been studied by a combination of multiple internal reflection Fourier transform infrared spectroscopy and computational investigations implementing density functional theory (DFT). Since the previously studied olefins have been shown to form a di-σ product on this surface following [2+2] cycloaddition, it was also initially expected for 2,3-dimethyl-2-butene. Infrared spectra taken at 100 K show that 2,3-dimethyl-2-butene adsorbs on the surface molecularly at this temperature. Heating the surface to room temperature left no indication of a chemisorbed product. Large doses at room temperature did not produce any observable absorption bands in the infrared spectrum, indicating that [2+2] cycloaddition of 2,3-dimethyl-2-butene does not occur. This assessment was verified by the Auger electron spectroscopy studies confirming that neither room temperature exposure nor annealing to 800 K produced any carbon remaining on this surface. These experimental observations of the absence of a chemical reaction between an olefin and a very reactive silicon surface were substantiated by DFT investigation of the adsorption kinetics. The formation of two possible π-bonded precursors was considered, and the energies required to form the di-σ-bonded product from either one of these precursors were predicted to be substantially higher than the desorption barrier. Thus, 2,3-dimethyl-2-butene is a unique olefin that is very inert with respect to the Si(100)-2×1 surface, making it a desirable carrier gas or a ligand in the precursor molecules in a number of deposition processes involving silicon substrates. View full abstract»

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  • The effectiveness of HCl and HF cleaning of Si0.85Ge0.15 surface

    Page(s): 1248 - 1250
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    The cleaning of Si0.85Ge0.15 surfaces using HCl and HF solutions is studied using synchrotron radiation photoelectron spectroscopy. The HF solution is found to be effective in removing both the Si oxide and the Ge oxide while the HCl solution can only remove part of the Ge oxide. For samples treated with HF, four spectral components are needed to fit the Ge 3d photoemission spectra. One is the bulk component and the other three are attributed to the surface Ge atoms with monohydride, dihydride, and trihydride terminations, respectively. 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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Meet Our Editors

G. Lucovsky
North Carolina State University