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May 2000

Volume 18, Issue 3, pp. 797-1047

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Characterization of magnetron-sputtered partially ionized deposition as a function of metal and gas species

Monica M. C. Allain, D. B. Hayden, D. R. Juliano, and D. N. Ruzic

J. Vac. Sci. Technol. A 18, 797 (2000); http://dx.doi.org/10.1116/1.582257 (5 pages) | Cited 6 times

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Conventional magnetron sputter deposition with a rf inductively coupled plasma (ICP) has demonstrated that ionized metal fluxes can be effectively utilized to fill trenches and vias with high aspect ratios. The ICP is created with a seven turn (1/2 wavelength), water cooled coil located between the magnetron cathode and the substrate. A large fraction of the metal atoms sputtered from the magnetron cathode are ionized by the ICP. These ions are accelerated across the sheath toward the substrate and deposited at normal incidence, by placing a negative bias on the substrate. A gridded energy analyzer configured with a quartz crystal microbalance is located in the center of the substrate plane to determine the ion and neutral deposition rates. While keeping the magnetron power, rf coil, target to substrate distance, pressure and diagnostic location constant, the ionization fraction was measured for two metal targets: Cu and Ti using three different working gases: Kr, Ar and Ne. Variations in target materials and working gases are shown to have an effect on ionization and deposition rates. The ionization rate is a sensitive function of the metal’s ionization potential. The electron energy distribution in the plasma is affected by the sputtered metal and the working gases’ ionization potential. © 2000 American Vacuum Society.
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81.15.Cd Deposition by sputtering
52.70.-m Plasma diagnostic techniques and instrumentation
52.25.-b Plasma properties
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Microstructural and morphological analysis of ultrathin YBa2Cu3O7−x films grown by modulated magnetron sputtering on SrTiO3 substrates

A. Del Vecchio, M. F. De Riccardis, L. Tapfer , C. Camerlingo, and M. Russo

J. Vac. Sci. Technol. A 18, 802 (2000); http://dx.doi.org/10.1116/1.582258 (7 pages) | Cited 2 times

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The defect structure, the degree of crystalline perfection and the surface roughness of HTc superconductor films are affected by the initial layer configuration at the early stage of growth. In this work we report on structural and morphological investigations of ultrathin YBa2Cu3O7−x films grown on SrTiO3 substrate. The films are fabricated by inverted cylindrical magnetron sputtering with a modified deposition process based on the modulation of sputtering power. The modulated sputtering deposition promotes a higher in-plane grain connectivity and allows us to fabricate films with a lower defect density. The structural analyses of very thin films (thickness <25 nm) are performed by using low-angle x-ray specular reflectivity, double crystal diffraction, reciprocal space mapping and atomic force microscopy. The results indicate that a total relaxation of our films occurs at layer thickness larger than 25 nm. For thinner layers a tetragonal distortion of the unit cell and no twinning are observed. The low-angle measurements show distinct Kiessig fringes revealing a smooth surface and film/substrate interface. The off-specular reflectivity measurements indicate that the surface and interface roughness across the YBa2Cu3O7−x layer are uncorrelated. © 2000 American Vacuum Society.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Cd Deposition by sputtering
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Diagnostics by optical absorption of sputtered atom density in magnetron discharges

M. F. Dony, J. P. Dauchot, M. Wautelet, M. Hecq, and A. Ricard

J. Vac. Sci. Technol. A 18, 809 (2000); http://dx.doi.org/10.1116/1.582259 (5 pages) | Cited 5 times

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Densities of sputtered atoms in Ar rf magnetron discharges have been measured by optical absorption. The resonant and self-absorption methods have been used. The first one has given Al and Mg atom densities with an uncertainty of 40% and the second one the order of magnitude of Si atom densities. The Al atom densities are strongly decreasing from 93.7% Al alloy target: (1–5)×1011 cm−3–10.3% Al aluminosilicate glass: (1–2)×109 cm−3. The Si atom density is in the range (3–9)×1010 cm−3 in the aluminosilicate glasses. The Al and Si sputtered atom densities follow the sputtering yields of Al metal and Al, Si oxide targets. © 2000 American Vacuum Society.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Influence of substrate temperature on the properties of indium oxide thin films

F. O. Adurodija, H. Izumi, T. Ishihara, H. Yoshioka, M. Motoyama, and K. Murai

J. Vac. Sci. Technol. A 18, 814 (2000); http://dx.doi.org/10.1116/1.582260 (5 pages) | Cited 17 times

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Pure indium oxide (In2O3) and SnO2-doped In2O3 (5 and 10 wt %) films were deposited on glass at different substrate temperatures (Ts) ranging from room temperature (RT=25 °C) to 350 °C using pulsed laser deposition. At low Ts (RT to 100 °C), pure In2O3 films yielded the lowest resistivity of (1.8–2.5)×10−4 Ω cm and the resistivity increased sharply with an increase in Ts, and the rise in the resistivity of pure In2O3 films resulted mainly from a decrease in carrier concentration and Hall mobility. For SnO2-doped In2O3 films, the resistivity decreased from 3.5×10−4 to 1.3×10−4 Ω cm with increasing Ts from RT to 350 °C and the reduction in the resistivity is associated with thermal activation of Sn leading to an increase in carrier concentration. Amorphous films were obtained at RT, but from Ts of 100 °C, the films appeared polycrystalline with orientation in the 〈111〉 plane. From atomic force microscopy, minimum surface roughness (Ra)⩽1.3 nm was obtained at RT and Ts>200 °C. Between 100 and 150 °C, Ra was maximum (2.5–4.9 nm). The films also exhibited high optical transmittance (>85%) to visible light. © 2000 American Vacuum Society.
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68.55.-a Thin film structure and morphology
73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
81.15.Fg Pulsed laser ablation deposition
81.05.Hd Other semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.40.Fy Semiconductors

Epitaxial growth structure and physical properties of Fe film biased dc-plasma sputter deposited on MgO(001)

Chang Chuan Chen, Jiping Yang, Hisashi Nakai, and Mituru Hashimoto

J. Vac. Sci. Technol. A 18, 819 (2000); http://dx.doi.org/10.1116/1.582261 (4 pages) | Cited 1 time

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One hundred-nm-thick Fe film has been deposited on MgO(001) substrate at 250 °C by biased dc-plasma sputtering at 2.9 kV in Ar gas. A dc bias voltage Vs between 0 and −160 V was applied to the substrate during deposition. Reflection high energy electron diffraction, x-ray diffraction, cross sectional transmission electron microscopy (XTEM) and high resolution XTEM were used to investigate the structure of the films. Electrical resistivity at room temperature was measured by four-point probe method. Saturation magnetization of the films at room temperature was measured using a vibration sample magnetometer. As a result, when Vs=−140 V the Fe film could be epitaxially grown with Fe(001)[110]//MgO(001)[100] while the film retained a polycrystalline structure when Vs was higher or lower than −140 V. The minimum electrical resistivity and the maximum saturation magnetization were achieved at Vs=−140 V consistent with the result of the growth structure. In conclusion, when Vs=−140 V the Fe film can be epitaxially grown with the lower defect density under the bombardment of energetic Ar particles accelerated by Vs to increase the mobility of Fe adatoms and to resputter impurity species during the film formation. © 2000 American Vacuum Society.
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81.15.Cd Deposition by sputtering
75.70.Ak Magnetic properties of monolayers and thin films
73.61.At Metal and metallic alloys
81.05.Bx Metals, semimetals, and alloys
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.-y Defects and impurities in crystals; microstructure

Optimization of plasma density and radial uniformity of a point-cusp magnetic field applied capacitive plasma

Sunil Wickramanayaka, Yukito Nakagawa, Yasumi Sago, and Yoichiro Numasawa

J. Vac. Sci. Technol. A 18, 823 (2000); http://dx.doi.org/10.1116/1.582262 (7 pages) | Cited 5 times

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A feasibility study in the development of a large area high-density plasma source with a higher radial plasma uniformity for large area wafer processing was carried out. Experiments were performed for 200 mm diameter wafers using parallel plate capacitively coupled plasma excited by 60 MHz radio frequency current. Point-cusp magnetic fields that can be easily expanded for 300 mm diameter wafer processing reactors without any technical difficulties are applied to the upper electrode. The point-cusp magnetic fields are generated by arranging 115 permanent magnets on a 266 mm diameter upper electrode with alternate polarity and equal distance. This arrangement of magnets produces a strong magnetic field at the surface of upper electrode and almost a magnetic field-free environment at around 40 mm below the upper electrode. This magnetic field also causes no polarization of the plasma due to the E×B drift of electrons where E and B are the direct current electric and magnetic field strengths, respectively. Application of the point-cusp magnetic field increases the plasma density by a factor of 2 and decreases the radial nonuniformity by a factor >1.5. The radial nonuniformity of the plasma at 58 mm below the upper electrode is further reduced to ±3.5% across the central 200 mm region by the application of a bucket magnetic field to the reactor sidewall and removing 16 magnets from the central region of the upper electrode. This latter change, however, slightly reduces the earlier explained plasma density increment. The radial uniformity of large area plasmas can be controlled with considerable ease by removing selected magnets from the central region of the upper electrode or reducing the magnetic field strength at the central region. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.70.Ds Electric and magnetic measurements
29.25.Ni Ion sources: positive and negative
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
52.25.-b Plasma properties

Depth distribution of plasma induced damage and dislocation generation due to an interaction of subsequent oxidation

T. Yamaguchi, T. Sasaki, H. Nikoh, and T. Ito

J. Vac. Sci. Technol. A 18, 830 (2000); http://dx.doi.org/10.1116/1.582263 (5 pages) | Cited 1 time

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Surface damage induced by reactive ion etching (RIE) was investigated in terms of its depth, distribution, and correlation with dislocation generation due to subsequent oxidation. Damage structure was evaluated using transmission electron microscopy, reflection high energy electron diffraction (RHEED), Auger electron spectroscopy, and thermal wave measurement technique. A chemical dry etching and surface analyze technique of RHEED and TW were utilized to profile the damage distribution. It is identified that the surface damaged layer consists of two parts; the upper part from the surface to about 4 nm is a heavily damaged amorphous structure containing carbon and the lower part, between 5 and 30 nm, is a single crystal Si with a lot of lattice defects. It is found that RIE damage may form film edge dislocations by the interaction of subsequent selective oxidation even though damage was minimized to suppress oxidation induced stacking faults generation. High leakage current occurs when n+–p junctions are fabricated on this RIE and selective oxidation because of these film edge dislocations. It seems that generation of film edge dislocations has correlated with this carbon contained amorphous layer. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
81.65.Mq Oxidation
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Nn Stacking faults and other planar or extended defects

Platinum etching using a TiO2 hard mask in an O2/Cl2/Ar plasma

Chee Won Chung and Ilsub Chung

J. Vac. Sci. Technol. A 18, 835 (2000); http://dx.doi.org/10.1116/1.582264 (5 pages) | Cited 11 times

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The dry etch behavior of Pt films using a TiO2 hard mask was investigated with an O2/Cl2/Ar gas chemistry in an inductively coupled plasma. The variations in etch rates and etch profiles of both the Pt films and the TiO2 masks were examined as a function of Cl2 and O2 concentration. It was found that the ratio of O2 to Cl2 concentration strongly influenced the etch selectivity of the Pt film relative to the TiO2 mask. X-ray photoelectron spectroscopy indicates that the addition of O2 to the gas mix causes a decrease in the TiO2 etch rate as a result of the oxidation of Ti2O3 and TiO species. It is proposed that these oxides arise via the reduction of TiO2 in the presence of a Cl2/Ar plasma. A 1 μm ×1 μm minimum feature size was successfully etched with this TiO2 mask material, yielding a sidewall of approximately 75° in slope that did not exhibit redeposition or residue. © 2000 American Vacuum Society.
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81.05.Bx Metals, semimetals, and alloys
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Large-diameter microwave plasma source excited by azimuthally symmetric surface waves

Mutumi Tuda, Kouichi Ono, Hiroki Ootera, Masaaki Tsuchihashi, Minoru Hanazaki, and Toshio Komemura

J. Vac. Sci. Technol. A 18, 840 (2000); http://dx.doi.org/10.1116/1.582265 (9 pages) | Cited 11 times

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This article describes a large-diameter, surface-wave excited plasma (SWP) source designed for materials processing. The plasma reactor employs a launcher of 2.45 GHz azimuthally symmetric surface waves in the field-free region of 24-pole line-cusp magnetic fields, generated by a set of permanent magnets surrounding the reactor chamber walls; the magnets also provide an electron cyclotron resonance (ECR) magnetic field of 875 G near the chamber wall surfaces. Langmuir probe and optical emission measurements were made for characterizing the plasma produced in Ar. After the microwave power was turned on, the discharge was observed to start near the ECR region and then propagate toward the field-free region in the central area of the chamber. Moreover, the discharge was also observed to be excited by ECR at low microwave-power levels, and by surface waves in the field-free region at above a critical power strongly depending on the gas pressure. Such a transition of plasma excitation from ECR to SWP was found to occur under conditions where the plasma electron density exceeds a 2.45 GHz microwave cutoff value of ≈7.4×1010 cm−3. As a result, overdense plasmas with large diameters could be successfully produced with moderate microwave input powers ≲1 kW; the electron density was measured to be Ne∼1−3.5×1011 cm−3 in Ar plasmas, with its spatial variation being ≲5% over a 26-cm-diam area. Furthermore, preliminary experiments of SiO2 etching in pure CF4 plasmas showed that the SiO2 etch rate was typically ∼300 nm/min with a good uniformity ≲3% over an 8-in.-diam wafer. © 2000 American Vacuum Society.
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52.50.Dg Plasma sources
52.25.-b Plasma properties
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.70.Ds Electric and magnetic measurements

Diagnostic studies of aluminum etching in an inductively coupled plasma system: Determination of electron temperatures and connections to plasma-induced damage

M. V. Malyshev, V. M. Donnelly, S. W. Downey, J. I. Colonell, and N. Layadi

J. Vac. Sci. Technol. A 18, 849 (2000); http://dx.doi.org/10.1116/1.582266 (11 pages) | Cited 14 times

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Using trace rare gases-optical emission spectroscopy (TRG-OES) and Langmuir probe measurements, electron temperatures (Te) were obtained in Cl2/BCl3/N2 plasmas in an inductively coupled plasma system, under typical processing conditions for metal etching. A small amount (1.7% each) of the five rare gases was added to the plasma and emission spectra were recorded. TRG-OES Tes corresponding to the high-energy tail of the electron energy distribution function were derived from the best match between the observed and computed rare gas emission intensities. Te was determined as a function of total pressure, source power, fraction of BCl3 added to Cl2 and substrate material (SiO2, Al, and photoresist). Positive ion densities and relative electron densities were also measured for some of these conditions. At source and bias powers of 1000 and 100 W, TRG-OES Tes in Cl2/BCl3/N2/rare gas plasmas increased from 1.4 eV at 40 mTorr to 2.3 eV at 3 mTorr, about 15% lower than values computed from a global model and ∼1.4 times lower than those measured with a Langmuir probe. Reduced plasma induced damage to the gate oxide at higher pressures (18 vs 10 mTorr) correlates with a drop in both Te (1.7 vs 1.9 eV) and plasma density (1.0×1011 vs 1.3×1011 cm−3), but is due mostly to the lower Te. © 2000 American Vacuum Society.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.-b Plasma properties

Simulation of the influence of the filament arrangement on the gas phase during hot filament chemical vapor deposition of diamond films

G. H. Song, C. Sun, R. F. Huang, and L. S. Wen

J. Vac. Sci. Technol. A 18, 860 (2000); http://dx.doi.org/10.1116/1.582267 (4 pages) | Cited 5 times

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The uniform temperature and mass current density of gas in deposition regions of films were very important to obtain uniform diamond films over a large area during hot filament chemical vapor deposition. The simulation showed that the two physical parameters of gas in the chamber varied as a function of space and were influenced by the arrangement of the filaments and the initial rate of the introduced gas. Regions of uniform temperature and mass current density existed in the chamber. The distributions of temperature and mass current density did not vary with the filament diameter. However, the value of the two physical parameters increased and declined with the increment of the diameter, respectively. An optimum distance between filaments was necessary to obtain uniform films over a large area. The mass current density increased with the initial rate of the introduced gas. These results might provide a basis for optimizing the technological parameters to obtain uniform diamond films over a large area. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors

Diagnostics of an inductively coupled CF4/Ar plasma

Kazuya Hioki, Hajime Hirata, Shosaku Matsumura, Zoran Lj. Petrović, and Toshiaki Makabe

J. Vac. Sci. Technol. A 18, 864 (2000); http://dx.doi.org/10.1116/1.582268 (9 pages) | Cited 22 times

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Experimental data for radiative and metastable state densities in pure argon and in mixture of 5% CF4 in argon are obtained to study the effect of CF4 on kinetics of inductively coupled plasma (ICP). The measurements were made by a combination of optical emission spectroscopy and computer tomography for radiative levels and by laser absorption for metastable state profiles. The data were obtained in an inductively coupled rf (13.56 MHz) plasma with a single coil and full cylindrical symmetry. At low pressures of 5 and 15 mTorr the data in pure argon and in the mixture do not differ much, both in the magnitude and in the radial and axial profiles. However, at 50, 100, and 300 mTorr there is a dramatic change when CF4 is introduced. The metastable density increases due to the smaller electron induced quenching while axial and radial profiles are quite different. Unfortunately introduction of CF4 spoils the degree of azimuthal isotropy. The observed results and explanations based on the important role of metastables and stepwise processes in kinetics of high electron density ICP are supported by measurements of plasma density by using a double probe. © 2000 American Vacuum Society.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.-b Plasma properties

Study of the effects of discharge conditions and substrate temperature on Si epitaxial deposition using sputtering-type electron cyclotron resonance plasma

Junsi Gao, Junli Wang, Naofumi Sakai, Kanako Iwanaga, Katsunori Muraoka, Hiroshi Nakashima, Dawei Gao, and Katsuhiko Furukawa

J. Vac. Sci. Technol. A 18, 873 (2000); http://dx.doi.org/10.1116/1.582269 (6 pages) | Cited 2 times

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It was found that epitaxial Si films could be deposited on Si substrates by using a sputtering-type electron cyclotron resonance plasma that had a conventional base pressure of 5×10−7 Torr. The effects of discharge conditions and substrate temperature were studied systematically in order to understand the necessary conditions for epitaxial growth. It was found that discharge gas pressure, target power for sputtering, and substrate temperature play crucial roles in the epitaxial deposition. The implications of the changes of the three parameters are discussed in detail. © 2000 American Vacuum Society.
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81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Cd Deposition by sputtering

Selective etching of GaN over AlN using an inductively coupled plasma and an O2/Cl2/Ar chemistry

S. A. Smith, W. V. Lampert, P. Rajagopal, A. D. Banks, D. Thomson, and R. F. Davis

J. Vac. Sci. Technol. A 18, 879 (2000); http://dx.doi.org/10.1116/1.582270 (3 pages) | Cited 4 times

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An alternative method for achieving etching selectivity between GaN and AlN has been demonstrated. The etch rate of AlN was significantly decreased by the addition of a low concentration of O2 to a Cl2–Ar mixture in an inductively coupled plasma (ICP) etching system. The etch rate of GaN in the O2-containing plasma was approximately 15% less than the plasma without the O2 for the same parameters. The pressure and the ICP power were varied to achieve a maximum selectivity of 48 at a pressure of 10 mTorr, a direct current bias of −150 V, and an ICP power of 500 W. The etch rates of GaN and AlN at these parameters were 4800 and 100 Å/min, respectively. © 2000 American Vacuum Society.
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81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Mass-resolved ion energy distributions in continuous dual mode microwave/radio frequency plasmas in argon and nitrogen

A. Hallil, O. Zabeida, M. R. Wertheimer, and L. Martinu

J. Vac. Sci. Technol. A 18, 882 (2000); http://dx.doi.org/10.1116/1.582271 (9 pages) | Cited 16 times

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The control of plasma-surface interactions in terms of synergistic effects of ions, photons, and chemically active species is important for the optimization of plasma enhanced chemical vapor deposition of thin films and for plasma-induced surface modification. In the present work, we use a dual-mode microwave/radio frequency (MW/rf) plasma system, in which we investigate the effect of plasma parameters (gas type and pressure, self-bias voltage, for example) on the energy and flux of ionic species arriving at the specimen surface. We determine the ion energy distribution functions (IEDFs) using a mass spectrometer/energy analyzer, in Ar and N2 discharges, excited at different frequencies. The results for Ar+, N2+, and N+ ions show structured IEDFs at the rf-powered electrode in the single- and dual-frequency modes, while a single peak is observed in the continuous MW plasma. The MW/rf plasma presents substantially higher ion flux and plasma density, and a much thinner sheath than the rf case. Changes in plasma impedance, measured by a rf current–voltage probe, support the results on plasma density and sheath thickness, determined from the IEDFs. The MW/rf discharge impedance displays a resistive behavior in contrast to rf plasma, where the impedance is capacitive. © 2000 American Vacuum Society.
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52.70.Nc Particle measurements
52.80.Pi High-frequency and RF discharges
52.70.Ds Electric and magnetic measurements
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.-b Plasma properties

Kinetic study of 3C-SiC growth on Si by pyrolyzing tetramethysilane in low pressure radio frequency-induction heated chemical vapor deposition reactor

Kwang Chul Kim, Kee Suk Nahm, Yoon Bong Hahn, Yeon Sik Lee, and Hun-Soo Byun

J. Vac. Sci. Technol. A 18, 891 (2000); http://dx.doi.org/10.1116/1.582272 (9 pages) | Cited 9 times

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Single crystal 3C-SiC films were grown on Si(111) substrate using tetramethylsilane [TMS,(CH3)4Si] in a low pressure radio frequency-induction heated chemical vapor deposition reactor. The growth rate of 3C-SiC film increased with increasing TMS flow rate and growth temperature. The growth kinetics of 3C-SiC film was determined by analyzing the experimental data on the growth rate. The growth reaction of 3C-SiC film was the first order of TMS partial pressure in the reactor. The reaction rate controlling step changed from the surface reaction in the temperature range of 1100–1250 °C to the diffusion of reactive gases at higher temperatures above 1250 °C. The activation energies were 72.2 kcal/min for the surface reaction-controlling step and 38.2 kcal/min for the diffusion-controlling step. At the growth temperatures, TMS was dissociated into hydrogen, Si atoms, and hydrocarbon gases such as CH3⋅, CH4, C2H2, and C2H4. The effective reactive species for the growth of 3C-SiC turned out to be gaseous Si atoms and methyl radicals in this growth system. The mechanisms of TMS decomposition and SiC growth were discussed in detail based on quadrapole mass spectrometer analysis. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Nq Composition and phase identification
81.05.Hd Other semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Adhesion improvement of cubic BN:C film synthesized by a helicon wave plasma chemical vapor deposition process

Kyoung-Bo Kim and Seon-Hyo Kim

J. Vac. Sci. Technol. A 18, 900 (2000); http://dx.doi.org/10.1116/1.582273 (7 pages) | Cited 2 times

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The growth and adhesion of cubic boron nitride:carbon (c-BN:C) film were investigated using Fourier transform infrared spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. c-BN:C films were prepared on a Si(111) substrate by a helicon wave plasma chemical vapor deposition process using borazine, methane, and hydrogen beyond the critical substrate bias and temperature of −250 V and 450 °C, respectively. The improved adhesion of c-BN:C film with the addition of CH4 and hydrogen resulted from the simultaneous reduction of residual compressive stress and nonbonded (free) boron reaction with atmospheric water vapor. In addition, postheat treatment at 800 °C could further reduce the residual compressive stress in the c-BN:C film. The repetition technique of the combinative process of carbon and hydrogen addition together with postheat treatment (multistep deposition method) enabled the growth of thick c-BN:C film of ∼1 μm. © 2000 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
81.65.-b Surface treatments
68.35.Gy Mechanical properties; surface strains
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.40.Gh Other heat and thermomechanical treatments

Monte Carlo simulation of vapor transport in physical vapor deposition of titanium

Jitendra Balakrishnan, Iain D. Boyd, and David G. Braun

J. Vac. Sci. Technol. A 18, 907 (2000); http://dx.doi.org/10.1116/1.582274 (10 pages) | Cited 6 times

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In this work, the direct simulation Monte Carlo (DSMC) method is used to model the physical vapor deposition of titanium using electron-beam evaporation. Titanium atoms are vaporized from a molten pool at a very high temperature and are accelerated collisionally to the deposition surface. The electronic excitation of the vapor is significant at the temperatures of interest. Energy transfer between the electronic and translational modes of energy affects the flow significantly. The electronic energy is modeled in the DSMC method and comparisons are made between simulations in which electronic energy is excluded from and included among the energy modes of particles. The experimentally measured deposition profile is also compared to the results of the simulations. It is concluded that electronic energy is an important factor to consider in the modeling of flows of this nature. The simulation results show good agreement with experimental data. © 2000 American Vacuum Society.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Bx Metals, semimetals, and alloys
68.55.-a Thin film structure and morphology

Titanium oxide films on Si(100) deposited by electron-beam evaporation at 250 °C

H. K. Jang, S. W. Whangbo, H. B. Kim, K. Y. Im, Y. S. Lee, I. W. Lyo, C. N. Whang, G. Kim, H.-S. Lee, and J. M. Lee

J. Vac. Sci. Technol. A 18, 917 (2000); http://dx.doi.org/10.1116/1.582275 (5 pages) | Cited 12 times

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Titanium oxide films with a thickness of a 400 nm were deposited on p-type Si(100) at 250 °C by electron-beam evaporation where titanium dioxide was evaporated in oxygen environment at a pressure of 2×10−6–4×10−5 Torr. Effects of oxygen flow rate (FO2) between 0 and 40 sccm on properties such as crystallinity, surface roughness, and chemical states of the films have been investigated. Oxygen resonance backscattering spectroscopy shows that all films are oxygen rich, i.e., the ratio of oxygen to titanium of the films ranged from 2.25 to 2.3. X-ray diffraction patterns show that these films grown at 250 °C are polycrystalline of anatase TiO2. Ti K-edge x-ray absorption near-edge spectroscopy (XANES) spectra show that the films have mixed phases of anatase and rutile TiO2. More than 70% of the films is anatase TiO2 and its proportion of the films is decreased with increasing FO2. XANES spectra from the films grown at FO2=0 sccm are very similar to that of the powdered anatase TiO2. X-ray photoelectron spectroscopy indicates that there exist Ti2+, Ti3+, and Ti4+ charge states in the film grown at FO2≦10 sccm but there exist only Ti3+ and Ti4+ charge states in the film grown at FO2>10 sccm. © 2000 American Vacuum Society.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.70.Dm X-ray absorption spectra
79.60.Dp Adsorbed layers and thin films

Nonisomorphic ErF3 layers on Si(111) substrates grown by molecular beam epitaxy

J. M. Ko, S. D. Durbin, T. Fukuda, and K. Inaba

J. Vac. Sci. Technol. A 18, 922 (2000); http://dx.doi.org/10.1116/1.582276 (5 pages)

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ErF3 layers were grown on Si(111) substrates at 400, 550, and 700 °C by molecular beam epitaxy. Reflection high-energy electron diffraction in situ and x-ray rocking curve analysis ex situ showed that at the high growth temperature of 700 °C, an ErF3 layer of the native orthorhombic structure could be grown conformably on the hexagonal atomic arrangement of the Si(111) substrate. The surface morphology and flatness of the resulting layers were studied by atomic force microscopy as a function of growth temperature and layer thickness. At higher temperatures, layers consist of highly perfect crystallites aligned with b axes normal to the substrate, and c axes along one of six symmetrically related 〈01math〉 directions of the Si substrate. © 2000 American Vacuum Society.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Plasma erosion of a magnesium radio-frequency cathode measured by laser-induced fluorescence

A. Brockhaus, A. Georg, V. Wingsch, and J. Engemann

J. Vac. Sci. Technol. A 18, 927 (2000); http://dx.doi.org/10.1116/1.582277 (6 pages) | Cited 1 time

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Various diagnostic methods are compared with respect to their abilities in determining the controlled electrode erosion in a radio-frequency (rf) plasma source. The source is cylindrical in shape with a center rf cathode made of magnesium. Due to the unequal electrode area ratio of 1:8 a high self-bias voltage develops. Sputtering from the cathode was studied by means of optical emission spectroscopy, laser-induced fluorescence (LIF), quadrupole mass spectrometry, and deposition experiments. Dependencies of the plasma parameters were measured. The magnesium density decreased exponentially with distance from the target but could be traced down to very low levels around 105 cm−3 in the downstream region by the extremely sensitive LIF method. Laser excitation from the electronic ground state as well as fluorescence detection were performed on the strong 3p 1P1o←3s 1S0 resonance line at 285.2 nm. For absolute calibration Rayleigh scattering from cold nitrogen gas was utilized. Sensitivity issues and detection limits are discussed. © 2000 American Vacuum Society.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Nc Particle measurements
07.77.Ka Charged-particle beam sources and detectors
52.40.Hf Plasma-material interactions; boundary layer effects

Design and preparation of a 33-layer optical reflection filter of TiO2–SiO2 system

Xinrong Wang, Hiroshi Masumoto, Yoshihiro Someno, Lidong Chen, and Toshio Hirai

J. Vac. Sci. Technol. A 18, 933 (2000); http://dx.doi.org/10.1116/1.582278 (5 pages) | Cited 2 times

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Multilayer optical reflection filters with several kinds of graded refractive index profiles were designed. The effects of the number of layers of multilayer films and grading functions of refractive index profiles on the optical filter characteristics were examined by using simulation. A 33-layer optical reflection filter with a linear refractive index profile was found to be optimal in terms of both optical performance and manufacture. The designed 33-layer TiO2–SiO2 reflection filter was fabricated by helicon plasma sputtering. The optical performance of the prepared multilayer film agreed well with that of the designed filter. The measured transmittance spectrum exhibited a sharp cutoff stop band around a central wavelength of 1340 nm and a wide pass region with high transmittance of about 90%. The reflectance of the stop band was greater than 99.0% in the wavelength region from 1208 to 1518 nm. © 2000 American Vacuum Society.
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42.79.Ry Gradient-index (GRIN) devices
42.79.Ci Filters, zone plates, and polarizers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Cd Deposition by sputtering

New C–F interatomic potential for molecular dynamics simulation of fluorocarbon film formation

J. Tanaka, C. F. Abrams, and D. B. Graves

J. Vac. Sci. Technol. A 18, 938 (2000); http://dx.doi.org/10.1116/1.582279 (8 pages) | Cited 37 times

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A new interatomic potential of fluorocarbon systems has been developed. This potential is based on Brenner’s reactive empirical bond-order potential [D. W. Brenner, Phys. Rev. B 42, 9458 (1990)] for hydrocarbon systems which is a variation of Tersoff potential [J. Tersoff, Phys. Rev. Lett. 56, 632 (1986)]. A set of empirical correction functions was determined so as to reproduce the accurate atomization energies of many types of fluorocarbon molecules. To check the transferability of Tersoff–Brenner potential to ion sputtering problems, molecular dynamics simulations were conducted. We thereby studied carbon sputtering by argon ions for the first time and obtained reasonable sputtering yield compared with experimental data. The fluorocarbon film formation on an amorphous carbon surface exposed to CFx+ (x=1,2,3) bombardments was also simulated with the new C–F potential. (The ion energy was 100 eV.) CF+ impacts continued to grow carbon-rich fluorocarbon film, but CF2+ ions formed a fluorocarbon film that was then etched down. And CF3+ ion impacts turned the deposition into etching more rapidly than CF2+. The composition of etching products changed according to the state of fluorocarbon films, and this change should be included in boundary conditions of macrolevel simulations. © 2000 American Vacuum Society.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Synergism of transmission measurements with spectroscopic ellipsometry measurements in the analysis of a nearly opaque bimetal film stack on glass

Harland G. Tompkins and Sonja Tasic

J. Vac. Sci. Technol. A 18, 946 (2000); http://dx.doi.org/10.1116/1.582280 (5 pages)

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For a bimetal stack (Pt) and (Au) which is nearly opaque, we used transmission measurements along with spectroscopic ellipsometry measurements to determine the thicknesses of each metal layer as well as the optical constants of both materials. The key role of the transmission measurements is discussed. © 2000 American Vacuum Society.
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78.66.Bz Metals and metallic alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Kc Metals, semimetals, and alloys

Atomic hydrogen-cleaned GaAs(100) negative electron affinity photocathode: Surface studies with reflection high-energy electron diffraction and quantum efficiency

K. A. Elamrawi, M. A. Hafez, and H. E. Elsayed-Ali

J. Vac. Sci. Technol. A 18, 951 (2000); http://dx.doi.org/10.1116/1.582281 (5 pages) | Cited 3 times

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The quantum efficiency of a vicinal GaAs(100) negative electron affinity (NEA) photocathode is studied and correlated to the surface morphology. Cleaning of a GaAs(100) vicinal surface by atomic hydrogen and by heating are investigated using reflection high-energy electron diffraction (RHEED). After atomic hydrogen cleaning at 500 °C, the GaAs surface exhibits a streaky (2×4)-reconstructed RHEED pattern. When the GaAs(100) surface is activated to NEA by the alternate deposition of cesium and oxygen, a quantum efficiency of ∼9% is measured. The photocathode quantum efficiency correlates with the out-of-phase RHEED intensity measured before activation. After the quantum efficiency decreases with operating time, further atomic hydrogen exposure also produces a (2×4) pattern. Surfaces prepared or revived by atomic hydrogen produce brighter out-of-phase electron diffraction patterns and, when activated to NEA, higher quantum efficiency compared to those that are heat cleaned. © 2000 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena

Excitons in ultrathin InAs/InP quantum wells: Interplay between extended and localized states

P. Paki, R. Leonelli, L. Isnard, and R. A. Masut

J. Vac. Sci. Technol. A 18, 956 (2000); http://dx.doi.org/10.1116/1.582282 (4 pages) | Cited 9 times

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We have performed detailed optical measurements of ultrathin InAs/InP quantum wells grown by metalorganic vapor phase epitaxy. Absorption and photoluminescence excitation spectra reveal the excitonic resonances associated with two- and three-monolayer-thick InAs layers. Photoluminescence spectra also show an emission band at intermediate photon energies which is associated with excitons localized in thin InAs quantum dots. Polarization-dependent measurements clearly show the heavy-hole or light-hole nature of the quantum well resonances. Such an identification of both type of transitions provides a test for electronic structure models. We find that the energy positions of the excitonic transitions in ultrathin InAs/InP quantum wells are not consistent with calculations based on the envelope function model. © 2000 American Vacuum Society.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.20.Fz Weak or Anderson localization

Surface diffusion of adsorbed Si atoms on the Si(111)7×7 surface studied by atom-tracking scanning tunneling microscopy

Tomoshige Sato, Shin’ichi Kitamura, and Masashi Iwatsuki

J. Vac. Sci. Technol. A 18, 960 (2000); http://dx.doi.org/10.1116/1.582283 (5 pages) | Cited 33 times

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The initial adsorption process of Si atoms deposited on a Si(111)7×7 surface has been investigated at 80 to 500 K using a variable-temperature scanning tunneling microscopy. At room temperature, adsorbed Si atoms spontaneously formed tetramers over the center dimers in the dimers adatoms and stacking fault model of a 7×7 structure. Many other adsorbed Si atoms, which were not used for the formation of tetramers, were observed to diffuse within each half of the 7×7 unit cell. The diffusion of Si atoms across the surface was examined directly by using an atom-tracking technique. At low temperatures, the adsorption position of the Si atom was found to depend only on the potential energy. At high temperatures, the activation energy of an Si atom beyond the boundary between the half-unit cells was measured as Ea=1.14 eV. © 2000 American Vacuum Society.
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68.35.Fx Diffusion; interface formation
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
61.72.Nn Stacking faults and other planar or extended defects

Residual stress in GaN epilayers grown on silicon substrates

Yankun Fu, Daniel A. Gulino, and Ryan Higgins

J. Vac. Sci. Technol. A 18, 965 (2000); http://dx.doi.org/10.1116/1.582284 (3 pages) | Cited 5 times

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GaN films on AlN buffer layers were grown on (111) silicon substrates in a vertical rotating disk metal–organic chemical-vapor deposition reactor (CVD, Inc.). The dependence of residual stress in GaN films on the V/III molar flow ratio was studied. The crystalline quality of GaN films was analyzed by x-ray diffractometry, and the x-ray lattice parameter method was used to determine the residual stress in the films by measuring the c-axis and a-axis strain separately. The x-ray results show that the residual stress decreases with an increasing V/III molar flow ratio if all other growth parameters are kept constant. © 2000 American Vacuum Society.
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68.60.Bs Mechanical and acoustical properties
81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Wide range temperature dependence of reflection high-energy electron diffraction rocking curve from a Si(111)7×7 surface

Y. Fukaya, K. Nakamura, and Y. Shigeta

J. Vac. Sci. Technol. A 18, 968 (2000); http://dx.doi.org/10.1116/1.582285 (4 pages) | Cited 5 times

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In order to determine the Debye parameter for the surface layer of Si crystal, we have measured the rocking curves of reflection high-energy electron diffraction (RHEED) from a Si(111)-7×7 surface at temperatures extending over a wide range, 293–1073 K. From the analysis of the dynamical calculation of RHEED intensity taking account of the thermal diffuse scattering, the adatoms and rest atoms largely shifted upward compared with the atomic positions derived by Brommer et al. using ab initio molecular-dynamics scheme [Phys. Rev. Lett. 68, 1355 (1992)] and the optimum Debye temperature has been estimated at 420 K, which is much lower than that of bulk Si (505–658 K). Since the Debye temperature is considered to be an averaged value in a few surface layers, the difference means that the vibrational amplitude of surface atom is large compared to bulk atom. © 2000 American Vacuum Society.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ja Surface and interface dynamics and vibrations
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
68.35.Rh Phase transitions and critical phenomena
71.15.-m Methods of electronic structure calculations

Influence of air exposures and thermal treatments on the secondary electron yield of copper

Iouri Bojko, Noël Hilleret, and Christian Scheuerlein

J. Vac. Sci. Technol. A 18, 972 (2000); http://dx.doi.org/10.1116/1.582286 (8 pages) | Cited 8 times

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The variation of the secondary electron yield (SEY) of sputter-cleaned oxygen-free high-conductivity copper has been studied as a function of air exposure duration at room temperature. After short air exposures of some seconds the maximum SEY (δmax) of clean copper is reduced from 1.3 to less than 1.2, due to the oxidation of the copper surface. Prolonged air exposure increases the SEY steadily until, after about 8 days of atmospheric exposure, δmax is higher than 2. Air exposures at higher temperatures have been found to be effective in reducing the SEY of technical copper surfaces. A 5 min air exposure of copper at 350 °C followed by a 350 °C bakeout under vacuum reduces δmax to about 1.05, which is lower than the value of pure copper and that of Cu2O. © 2000 American Vacuum Society.
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79.20.Hx Electron impact: secondary emission
81.65.Mq Oxidation
81.40.Gh Other heat and thermomechanical treatments
81.05.Bx Metals, semimetals, and alloys

Stress, microstructure, and stability of Mo/Si, W/Si, and Mo/C multilayer films

David L. Windt

J. Vac. Sci. Technol. A 18, 980 (2000); http://dx.doi.org/10.1116/1.582287 (12 pages) | Cited 11 times

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The stresses in periodic Mo/Si, W/Si, and Mo/C multilayer films were determined from wafer-curvature measurements. The layer thickness of each material was varied systematically, and parametric stress contours were generated, showing contours of constant stress in the two-dimensional layer thickness parameter space. These results illustrate that the net stress in a periodic multilayer is not an intrinsic property of the film (for specific deposition conditions) but, rather, depends strongly on the individual layer thicknesses. X-ray diffraction measurements show (a) how the lattice spacing in the W and Mo crystallites varies with layer thickness, and (b) in the case of the W/Si films, how the phase composition of the polycrystalline W layers vary with W layer thickness. In the case of the W/Si and Mo/Si multilayers, irreversible stress changes were observed after the samples were stored in air at room temperature for a period of several months. Stress–temperature measurements made on the as-deposited W/Si and Mo/Si samples also reveal irreversible stress changes (both positive and negative, depending on the layer thicknesses) after thermal cycling to 300 °C; x-ray diffraction measurements were used to identify any associated changes in the W and Mo microstructure. We describe mechanisms that can explain the observed stress behavior, and also discuss the significance of these results, particularly with regard to the use of these films for high-performance multilayer x-ray optics. © 2000 American Vacuum Society.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Ct Interface structure and roughness
81.40.Gh Other heat and thermomechanical treatments
68.35.Gy Mechanical properties; surface strains

Delivery of pure ozone in ultrahigh vacuum

V. Zhukov, I. Popova, and J. T. Yates

J. Vac. Sci. Technol. A 18, 992 (2000); http://dx.doi.org/10.1116/1.582288 (3 pages) | Cited 7 times

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An apparatus designed to produce and deliver pure ozone to a sample inside a metal ultrahigh vacuum apparatus is described. Ozone of 96%–97% purity is prepared in a glass vacuum system and converted to a molecular beam of known flux using an all glass doser. The storage lifetime of the O3 at Torr pressure in the glass storage vacuum system (containing a small surface area of metal) has been measured, and it is shown that the rate of O3 destruction during storage is inconsequential for hours of storage. © 2000 American Vacuum Society.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.77.Gx Atomic and molecular beam sources and detectors
37.20.+j Atomic and molecular beam sources and techniques
34.50.Lf Chemical reactions
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Novel method for absolute quantification of the flux and angular distribution of a radical source for atomic hydrogen

T. Schwarz-Selinger, A. von Keudell, and W. Jacob

J. Vac. Sci. Technol. A 18, 995 (2000); http://dx.doi.org/10.1116/1.582289 (7 pages) | Cited 34 times

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In this article we present a novel method for absolute quantification of the flux and angular distribution of a beam source for atomic hydrogen or atomic deuterium. It is based on quantitative determination of the erosion of an amorphous, hydrogenated carbon (a-C:H) film. A heated tungsten capillary serves as the radical source. Atomic hydrogen is produced in this capillary by thermal dissociation of hydrogen molecules. A large-area a-C:H film is exposed to the source at a substrate temperature of 650 K. Interaction of atomic hydrogen with the a-C:H film causes erosion. From the spatial variation of the erosion rate one can deduce the angular distribution of the impinging hydrogen atoms. This angular distribution was also measured by mass spectrometry and showed excellent agreement with the erosion profile. The absolute flux of atomic hydrogen was also determined by mass spectrometry. With the absolute flux of atomic hydrogen known from mass spectrometry, measurement of the lateral variation of the erosion rate can be directly used as a probe for absolute quantification of the angular distribution of the impinging H (D) flux. The erosion yield is (2±0.7)×10−2, which is consistent with the microscopic erosion mechanisms of a-C:H by atomic hydrogen known from the literature. © 2000 American Vacuum Society.
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07.77.Gx Atomic and molecular beam sources and detectors
61.82.-d Radiation effects on specific materials
61.80.Lj Atom and molecule irradiation effects
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
29.25.-t Particle sources and targets

Low noise bipolar complementary metal–oxide–semiconductor mixer for radio frequency applications

S. Colomines, T. Parra, J. Graffeuil, and R. Plana

J. Vac. Sci. Technol. A 18, 1002 (2000); http://dx.doi.org/10.1116/1.582290 (4 pages)

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This article presents a low IF mixer featuring metal–oxide–semiconductor devices in the rf and the active load stages for DCS applications which have been optimized with respect to the supply voltage (2.2 V), current consumption (<10 mA), gain (10 dB), linearity (IIP3=8.5 dBm), and noise (DSB Nf=13 dB at 100 kHz). Special attention has been paid to the identification of the noise mechanisms. © 2000 American Vacuum Society.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
84.40.Dc Microwave circuits
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.40.Lj Microwave integrated electronics
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Modeling and characterization of logarithmic complementary metal–oxide–semiconductor active pixel sensors

Muahel Tabet, Nick Tu, and Richard Hornsey

J. Vac. Sci. Technol. A 18, 1006 (2000); http://dx.doi.org/10.1116/1.582291 (4 pages) | Cited 2 times

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We present a detailed analysis of logarithmic active pixel sensors (log-APS) to be used in complementary metal–oxide–semiconductor (CMOS) imagers for real-time on-chip motion detection. Based on an equivalent circuit model for CMOS-compatible photodiodes, an HSPICE simulation has been used to characterize different configurations of these sensors under various conditions of light intensities and switching speeds. These investigations are supported by the experimental results obtained from the chip fabricated with standard 0.5 μm CMOS technology. It is concluded that more robust on-chip motion detection in CMOS imagers can be achieved with careful design of its log-APS photocircuits that considers the issues discussed here.© 2000 American Vacuum Society.
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85.30.Tv Field effect devices
42.79.Pw Imaging detectors and sensors
85.30.De Semiconductor-device characterization, design, and modeling

Real time scanning tunneling microscopy study of the initial stages of oxidation of Ni(111) between 400 and 470 K

S. Hildebrandt, Ch. Hagendorf, T. Doege, Ch. Jeckstiess, R. Kulla, H. Neddermeyer, and Th. Uttich

J. Vac. Sci. Technol. A 18, 1010 (2000); http://dx.doi.org/10.1116/1.582292 (6 pages) | Cited 17 times

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A real-time in situ study of the initial stages of the interaction of oxygen with Ni(111) in a high temperature scanning tunneling microscope (STM) at temperatures between 400 and 470 K is presented. Oxygen adsorption features, in particular the Ni(111)-p(2×2)O reconstruction, were identified in room temperature STM images. The process of oxide formation is investigated in detail at 470 K. Starting from the initial nucleation at the step edges, a gradual transformation of the terrace structure results in the formation of a three-domain NiO(001) layer finally covering the entire terraces as well as forming bulges at the steps due to surface diffusion of excess Ni. Well-resolved local oxide surface structures are discussed on the basis of a thin (001)-oriented NiO layer model on the Ni(111) substrate. Formation of triangular bulk NiO(111) islands is observed for higher oxygen exposures above 25 L. © 2000 American Vacuum Society.
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81.65.Mq Oxidation
81.05.Bx Metals, semimetals, and alloys
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.55.-a Thin film structure and morphology
81.15.Aa Theory and models of film growth
68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena

Designs, analyses, and tests of a spiral-grooved turbobooster pump

Rong-Yuan Jou, Hong-Ping Cheng, Yu-Wen Chang, Fong-Zhi Chen, and Matsume Iwane

J. Vac. Sci. Technol. A 18, 1016 (2000); http://dx.doi.org/10.1116/1.582293 (9 pages) | Cited 5 times

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This article shows a spiral-grooved turbobooster pump, which has a momentum transfer-type vacuum pump function, and is capable of operation in a discharge pressure range up to 1000 Pa. Transitional flow pumping speeds are improved by a well-designed midsection element. Pumping performance of this new pump is predicted and examined by both of the computational fluid dynamics method and the direct simulation Monte Carlo method. These two complementary approaches are successfully being used to investigate the whole pumping speed curve from the viscous high-pressure to the molecular low-pressure range. Also, the developed pump is tested on an evaluation system constructed according to JVIS-005 standard. Good agreement between analytical results and experimental data are shown. Furthermore, to achieve a clean, safe, and reliable pumping process, this pump is designed with and operated by an innovative digital magnetic-bearing system. © 2000 American Vacuum Society.
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07.30.Cy Vacuum pumps
02.50.Ng Distribution theory and Monte Carlo studies
02.70.Rr General statistical methods
47.11.-j Computational methods in fluid dynamics
06.60.Mr Testing and inspecting procedures

Molecular transition and slip flows in the pumping channels of drag pumps

Joong-Sik Heo and Young-Kyu Hwang

J. Vac. Sci. Technol. A 18, 1025 (2000); http://dx.doi.org/10.1116/1.582294 (10 pages) | Cited 8 times

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Numerical and experimental investigations are performed for the molecular transition and slip flows in pumping channels of a helical-type drag pump (HTDP) and disk-type drag pump (DTDP). The flow occuring in the pumping channel develops from the molecular transition to slip flow traveling downstream. Two different numerical methods are used in this analysis: the first one is a continuum approach in solving the Navier–Stokes equations with slip boundary conditions, and the second one is a stochastic particle approach through the use of the direct-simulation Monte Carlo method. From the present study of a HTDP, the numerical results of predicting the performance, obtained by both methods, agree well with the experimental data for the range of Knudsen number Kn⩽0.01 (i.e., the slip-flow regime). But the results from the second method only agree with the experimental data for Kn>0.01 (i.e., the molecular-transition regime). From the analysis for a DTDP, we found that an actual pumping passage is strictly limited to a narrow region because of the significant backstreaming of molecules from the outlet. © 2000 American Vacuum Society.
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07.30.Cy Vacuum pumps
47.45.Gx Slip flows and accommodation
02.50.Ng Distribution theory and Monte Carlo studies
02.70.Rr General statistical methods
05.10.Gg Stochastic analysis methods (Fokker-Planck, Langevin, etc.)
47.60.-i Flow phenomena in quasi-one-dimensional systems
47.11.-j Computational methods in fluid dynamics
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Evacuating flat glass panels

R. E. Collins, M. Lenzen, and N. Ng

J. Vac. Sci. Technol. A 18, 1035 (2000); http://dx.doi.org/10.1116/1.582295 (3 pages)

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A method of evacuating flat glass panels through a small pumpout tube is described. In order to avoid breakage, the end of this pumpout tube, which is located outside a bakeout oven, has to be mounted in an O-ring fitting, which exerts little force on the tube during evacuation and bakeout. This is achieved first by allowing axial movement of the tube within the O-ring fitting, and second by attaching the vacuum fitting to a bracket, which in turn is fixed to a metal vacuum cup on the glass panel inside the oven. This method has several advantages over conventional evacuation techniques, including enabling the pumpout tube to be situated in a protected location in the edge of the glass panel, and permitting the panel to be baked at high temperatures. © 2000 American Vacuum Society.
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07.30.Bx Degasification, residual gas
07.30.Cy Vacuum pumps

Microhardness and structural analysis of (Ti,Al)N, (Ti,Cr)N, (Ti,Zr)N and (Ti,V)N films

Hiroyuki Hasegawa, Ayako Kimura, and Tetsuya Suzuki

J. Vac. Sci. Technol. A 18, 1038 (2000); http://dx.doi.org/10.1116/1.582296 (3 pages) | Cited 31 times

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Ti-based binary nitride and ternary nitride films were deposited on cemented carbide by the arc ion plating method and investigated on microhardness, lattice parameter and morphology. Micro-Vickers hardness of TiN, CrN, and ZrN binary films was 2000, 1400, and 1500 HV, respectively. On the other hand, ternary nitrides such as (Ti,Al)N, (TiCr)N, (Ti,Zr)N, and (Ti,V)N with identical atomic ratio against Ti generally had higher hardness of 3100, 3000, 3000, and 2400 HV, respectively. The lattice parameters of both (Ti,Al)N and (Ti,Cr)N were smaller with 4.18 and 4.19 Å. Futhermore, the surface roughness of TiN, CrN, ZrN, (TiAl)N, and (TiZr)N films was all smooth with small number of droplets, while that of (Ti,Cr)N and (Ti,V)N films became rough with large number of droplets. © 2000 American Vacuum Society.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.35.Gy Mechanical properties; surface strains
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
62.20.Qp Friction, tribology, and hardness

Patterning of polycrystalline diamond thin films on a variety of substrates by selectively seeding with purified ultrafine diamond powder

H. W. Liu, C. X. Gao, X. Li, C. X. Wang, Y. H. Han, G. T. Zou, W. K. Wang, L. L. Sun, and C. Wen

J. Vac. Sci. Technol. A 18, 1041 (2000); http://dx.doi.org/10.1116/1.582297 (4 pages) | Cited 1 time

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© 2000 American Vacuum Society.
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81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Cf Surface cleaning, etching, patterning
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A gradational lead screw dry vacuum pump

I. Akutsu, T. Matsuoka, M. Ozaki, T. Kyuko, S. Miyashita, T. Ozawa, M. Naka, H. Ohnishi, Y. Narahara, and G. Horikoshi

J. Vac. Sci. Technol. A 18, 1045 (2000); http://dx.doi.org/10.1116/1.582298 (3 pages)

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Abstract Unavailable
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07.30.Cy Vacuum pumps
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