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Nov 2001

Volume 19, Issue 6, pp. 2717-2986

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Vibrational spectroscopy of interfaces by infrared–visible sum frequency generation

M. Buck and M. Himmelhaus

J. Vac. Sci. Technol. A 19, 2717 (2001); http://dx.doi.org/10.1116/1.1414120 (20 pages) | Cited 58 times

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During the past decade vibrational sum frequency generation as a method to study interfaces has matured and can now be applied more routinely to systems of increasing complexity. The article provides a brief overview of technical aspects of infrared–visible sum frequency generation, compares this nonlinear technique with its linear analogs, and highlights the latest applications. © 2001 American Vacuum Society.
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68.35.Ja Surface and interface dynamics and vibrations
78.30.-j Infrared and Raman spectra
78.40.-q Absorption and reflection spectra: visible and ultraviolet
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
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Impression of high voltage pulses on substrate in pulsed laser deposition

T. Ikegami, M. Nakao, T. Ohsima, K. Ebihara, and S. Aoqui

J. Vac. Sci. Technol. A 19, 2737 (2001); http://dx.doi.org/10.1116/1.1401744 (4 pages) | Cited 1 time

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We report deposition of diamondlike carbon (DLC) films on silicon substrates in vacuum by ablating a graphite target using KrF excimer laser. High voltage pulses synchronous with the ablating laser pulse were applied to substrates to improve the hardness and adhesion of the DLC film. Ions accelerated in the carbon plasma plume resulted in an increase of ion flux and energy that modified the film properties. The effect of high voltage pulses on the laser ablated plasma plume was investigated by the laser induced fluorescence method, and their effect on DLC films was examined using Fourier transform infrared atomic force microscopy, and nanoindentation. High voltage pulse applied to the substrate increased the sp3 constituent in the DLC film and enhanced the smoothness and hardness of the film. © 2001 American Vacuum Society.
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81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
81.05.U- Carbon/carbon-based materials
68.35.Np Adhesion
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Pq Friction, lubrication, and wear
81.65.Kn Corrosion protection
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators

Video analysis of inclusion induced macroparticle emission from aluminum sputtering targets

C. E. Wickersham, J. E. Poole, J. S. Fan, and L. Zhu

J. Vac. Sci. Technol. A 19, 2741 (2001); http://dx.doi.org/10.1116/1.1403718 (10 pages) | Cited 2 times

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Molten metal macroparticles emitted from the surface of aluminum sputtering targets during arcing events is an important source of particulate contamination in sputtering. We used high-speed video analysis of arcing from sputtering targets purposefully doped with aluminum oxide inclusions to determine the velocity, trajectory, and relative size of the emitted macroparticles. The results of these analyses show that the molten droplets of aluminum are emitted from the target with velocities ranging from 5 to over 500 m/s. Ejection angles for the observed macroparticles were concentrated at angles of around 30° from the target plane. We also found that only certain arcing events generated video detectable macroparticle emission (∼18% of the arc events). Macroparticle size and velocity did not appear to be related. An estimate of macroparticle temperature based upon the sensitivity of the charge coupled device camera and the observed lack of macroparticle cooling yields an aluminum macroparticle temperature between 1750 and 4000 K. One cathode arc spot was observed on the target surface and the decay in intensity of this spot was used to estimate the cathode arc spot temperature. The cooling rate of a cathode arc spot on the target surface indicated that the arc spot cools by radiation and diffusion and has an initial temperature of 3000 K. This value is consistent with the macroparticle-estimated temperature of 3000±1000 K. © 2001 American Vacuum Society.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.05.Bx Metals, semimetals, and alloys
81.65.-b Surface treatments
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.35.Dv Composition, segregation; defects and impurities

Spectroscopic study of plasma using zirconium tetra-tert-butoxide for the plasma enhanced chemical vapor deposition of zirconium oxide

Byeong-Ok Cho, Sandy Lao, Lin Sha, and Jane P. Chang

J. Vac. Sci. Technol. A 19, 2751 (2001); http://dx.doi.org/10.1116/1.1403717 (11 pages) | Cited 23 times

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Plasma enhanced chemical vapor deposition of zirconium oxide using zirconium tetra-tert-butoxide (ZTB) as a metalorganic precursor, Ar as a carrier of the ZTB vapor, and O2 as an oxidant was investigated by using optical emission spectroscopy (OES), Langmuir probe, and x-ray photoelectron spectroscopy (XPS). The electron temperature (Te) and the O2 to Ar flow rate ratio (O2/Ar) were found to dominate the plasma chemistry: the Te determined the maximum Zr and Zr+ emission intensities at an intermediate pressure of 45 mTorr, the high C/C2 emission intensity ratio in the oxygen-rich plasma, and the transition between the dissociation-dominated chemistry at low pressures and the recombination-dominated chemistry at high pressures. The O2/Ar ratio changed the relative abundance of various atomic and diatomic species in the plasma: both ionic and atomic Zr species were depleted with the addition of O2 and a significant amount of ZrO and CO was produced. The O2/Ar ratio and Te determined the concentration ratio of C/O and C2/O in the plasma, the production and dissociation rates of diatomic molecules (C2, CH, CO, and OH), and the degree of decomposition. From XPS, x-ray diffraction, and OES measurements, the deposited ZrO2 was found to be stoichiometric and amorphous at O2/Ar ratios ⩾0.2, and hydrocarbon molecules rather than atomic carbon were more responsible for the carbon incorporation into the film. The carbon content in the film could be controlled by monitoring and varying the OES intensity ratio of C2 at 516.52 nm to O at 777.42 nm. © 2001 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
82.33.Ya Chemistry of MOCVD and other vapor deposition methods
79.60.Dp Adsorbed layers and thin films
52.70.Ds Electric and magnetic measurements
78.55.Hx Other solid inorganic materials
78.66.Nk Insulators

Development of tin oxide synthesis by plasma-enhanced chemical vapor deposition

Joshua J. Robbins, Robert T. Alexander, Mailasu Bai, Yen-Jung Huang, Tyrone L. Vincent, and Colin A. Wolden

J. Vac. Sci. Technol. A 19, 2762 (2001); http://dx.doi.org/10.1116/1.1403716 (5 pages) | Cited 5 times

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Transparent conducting oxide (TCO) thin films have been synthesized to date primarily by either physical vapor deposition or thermal chemical vapor deposition. Plasma-enhanced chemical vapor deposition (PECVD) offers potential advantages over these techniques, but it has not been applied extensively to TCO synthesis. In this article we report on the use of PECVD to deposit transparent, conducting tin oxide films from mixtures of SnCl4 and O2. These films were deposited on glass substrates at temperatures between 150 and 350 °C. The growth rate, optical, electrical, and structural properties were examined as a function of plasma power, substrate temperature, and gas composition. Increasing rf power revealed a rise in deposition rate with no effect on electrical properties, while both substrate temperature and oxygen flow rate were found to significantly influence resistivity. The effect of annealing was also examined, and it was found that annealing at 250 °C significantly improved the electrical properties. The optical transparency of all films was greater than 86% in the visible spectrum, and electrical resistivities as low as 2.1×10−3 Ω cm have been achieved. © 2001 American Vacuum Society.
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52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing
81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology

Measurements of the critical inclusion size for arcing and macroparticle ejection from aluminum sputtering targets

C. E. Wickersham, J. E. Poole, A. Leybovich, and L. Zhu

J. Vac. Sci. Technol. A 19, 2767 (2001); http://dx.doi.org/10.1116/1.1403719 (6 pages) | Cited 2 times

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Arcing during sputtering is a significant cause of defect generation during sputter deposition of thin films. We studied the effect of dielectric inclusion size on the propensity for arcing while sputtering aluminum targets in argon at power densities ranging from 8 to near 60 W/cm2. We found that there is a critical inclusion size required for arcing to occur. The critical size for an Al2O3 inclusion in an aluminum-sputtering target in an argon plasma is 440±160 μm. Inclusions with sizes above this critical value readily induce arcing and macroparticle ejection during sputtering. Inclusions below this critical size do not cause arcing or macroparticle ejection. We also found that the inclusion critical size was not sensitive to the sputtering power density. When the inclusion size exceeds the critical value the plasma boundary over the inclusion is deformed by the charge accumulating on the dielectric inclusion and the plasma positive column diffuses toward the target leading to a bipolar arc. Inclusions below the critical size do not distort the dark space to an extent great enough to permit bipolar arc formation. Our proposed model predicts that the critical inclusion size depends upon the sheath thickness, which ranged between 300 and 600 μm for the experimental conditions used in this study. © 2001 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Plasma immersion ion cleaning of oxidized steel surfaces using hexafluoroethane and argon plasmas

A. M. Peters and M. Nastasi

J. Vac. Sci. Technol. A 19, 2773 (2001); http://dx.doi.org/10.1116/1.1403720 (6 pages) | Cited 2 times

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For many years it has been known that cleaning of substrates using plasma techniques prior to physical vapor deposition processes can significantly improve coating adhesion. This article investigates the use of hexafluoroethane and argon plasmas in a pulsed glow discharge cleaning process. Applied voltages varied from −2 to −8 kV with a constant chamber pressure of 10 mTorr and etching times ranged from 15 to 120 min. Results indicate that in most cases, the hexafluoroethane plasmas removed 25% more oxygen atoms than the argon plasmas at similar applied voltages. Most of the oxygen removal was observed within the first 15 min with diminishing removal with increased cleaning time beyond 30 min. Plasma analysis revealed that the principal plasma specie was CF3 and reaction products for oxygen removal were carbon dioxide and carbon monoxide. The hexafluoroethane plasmas were determined to clean through a chemically enhanced sputtering while argon plasmas cleaned by physical sputtering only. © 2001 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.Np Adhesion

Crystallization kinetics in amorphous (Zr0.62Al0.38)O1.8 thin films

R. B. van Dover, D. V. Lang, M. L. Green, and L. Manchanda

J. Vac. Sci. Technol. A 19, 2779 (2001); http://dx.doi.org/10.1116/1.1403715 (6 pages) | Cited 12 times

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Thin films of Zr0.62Al0.38O1.8 are amorphous when deposited at room temperature by rf magnetron sputtering. Crystallization occurs during subsequent annealing in the temperature range of 700–1000 °C for times in the range of 10 s–100 h. The crystallite size and the fraction of the sample that had crystallized were determined using x-ray diffraction. The films were found to initially develop a low density of fairly large (∼8 nm) crystallites, while subsequent heat treatment was found to increase the density rather than the size of the crystallites. Crystallization can be described with a first-order rate equation; the rate constant is exponential in temperature with an effective activation energy of 6.6 eV. Films given a 10 s anneal at <850 °C develop a substantial density of 8 nm grains, making this specific composition an unsuitable candidate for replacing SiO2 as the gate oxide in hyperscaled field-effect transistors. © 2001 American Vacuum Society.
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68.55.-a Thin film structure and morphology
61.43.Er Other amorphous solids
61.72.Cc Kinetics of defect formation and annealing

Modeling of the slip flow in the spiral grooves of a molecular pump

Yeng-Yung Tsui, Chia-Ping Kung, and Hong-Ping Cheng

J. Vac. Sci. Technol. A 19, 2785 (2001); http://dx.doi.org/10.1116/1.1405510 (6 pages) | Cited 1 time

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A numerical methodology is applied to investigate the flow in the channels of a molecular pump in the slip flow regime. Both the slip and the no-slip boundary conditions are used to examine their effects on the flow field and the pumping performance. Also compared is the use of a rectangular channel model and a spiral channel model. In the latter model the flow channels are placed on the rotor of the pump while the former is sited on a stationary frame. It is shown that, by comparing with the no-slip condition, the slip condition leads to a weaker reverse flow in the channel and lower compression ratio. The results of the rectangular model are close to those of the spiral model, although there exists a minor degree of difference. This demonstrates that the rotational effects can be neglected. It is shown from the analysis that a pressure gradient in the circumferential direction is caused by the diffusion of the circumferential shear stress in the radial direction. However, by the present models the resulted pressure difference between the two side walls of the flow channel remains almost as a constant, irrespective of the flow rates. This is not true in the real flow. © 2001 American Vacuum Society.
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47.45.Gx Slip flows and accommodation
07.30.Cy Vacuum pumps

Direct correlation of x-ray photoelectron spectroscopy and Fourier transform infrared spectra and images from poly(vinyl chloride)/poly(methyl methacrylate) polymer blends

K. Artyushkova, B. Wall, J. Koenig, and J. E. Fulghum

J. Vac. Sci. Technol. A 19, 2791 (2001); http://dx.doi.org/10.1116/1.1405512 (9 pages) | Cited 6 times

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Correlative x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) studies of the complex heterogeneous structure of 50/50 poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) polymer blends are presented. The comparable lateral resolution and parallel (real-time) imaging capabilities of both techniques allow for a direct comparison of surface (XPS) and bulk (FTIR) measurements of polymer blends. To eliminate substrate influence and film-to-film differences, the same areas on the polymer films are analyzed by both methods. The effect of PMMA molecular weight on phase separation and surface segregation is evaluated using six blends with a constant PVC molecular weight and a PMMA molecular weight varying from 75 to 2132 kDa. Imaging capabilities of both methods are used for a qualitative comparison of the heterogeneous structure of the blends, while a quantitative comparison of the bulk and surface compositions of the same areas of the samples used small area spectroscopy from XPS and FTIR. Based on the small area quantitative analysis, it is concluded that surface segregation of PMMA increases with increasing molecular weight. This combination of small and large area correlative analyses in the determination of both surface and bulk properties of these heterogeneous polymer films leads to a more complete understanding of structure of complex samples. © 2001 American Vacuum Society.
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61.41.+e Polymers, elastomers, and plastics
79.60.Fr Polymers; organic compounds
78.66.Qn Polymers; organic compounds
78.30.Jw Organic compounds, polymers

Spectroscopic ellipsometry measurements of chromium nitride coatings

S. M. Aouadi, D. M. Mihut, M. L. Kuruppu, S. R. Kirkpatrick, and S. L. Rohde

J. Vac. Sci. Technol. A 19, 2800 (2001); http://dx.doi.org/10.1116/1.1405513 (5 pages) | Cited 5 times

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Coatings of chromium and chromium nitride with various compositions were deposited on silicon substrates using ion-assisted reactive magnetron sputtering. These coatings were characterized using x-ray diffraction (XRD), Rutherford backscattering (RBS), and spectroscopic ellipsometry (SE). The primary chromium nitride phases (Cr2N and CrN) in the chromium nitride films were identified using XRD. The chemical composition of selected samples was determined from RBS measurements. The refractive indices of Cr, Cr2N, and CrN were deduced from the analysis of the SE data. Based on these refractive indices, ellipsometry was used successfully to identify the microstructure and the roughness of a number of chromium nitride coatings grown under different deposition conditions. © 2001 American Vacuum Society.
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68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
78.66.Bz Metals and metallic alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.61.At Metal and metallic alloys
07.60.Fs Polarimeters and ellipsometers
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
81.15.Cd Deposition by sputtering
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

Estimates of differential sputtering yields for deposition applications

M. Stepanova and S. K. Dew

J. Vac. Sci. Technol. A 19, 2805 (2001); http://dx.doi.org/10.1116/1.1405515 (12 pages) | Cited 15 times

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Angular and angle-resolved energy distributions of neutral atoms sputtered from elemental targets under ion bombardment are investigated by numerical and analytic modeling. Special emphasis is made on sub-keV ion bombardment, which is typical for sputter deposition sources. Scaling laws that define the distribution anisotropies are formulated. An approximate semiempirical description is suggested for anisotropic energy distributions. © 2001 American Vacuum Society.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Cd Deposition by sputtering
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Deposition of amorphous and microcrystalline silicon using a graphite filament in the hot wire chemical vapor deposition technique

Scott Morrison and Arun Madan

J. Vac. Sci. Technol. A 19, 2817 (2001); http://dx.doi.org/10.1116/1.1405514 (3 pages) | Cited 3 times

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The use of a graphite filament in the “hot wire” chemical vapor deposition technique is demonstrated to produce “state-of-the-art” intrinsic and doped (p- and n-) amorphous silicon (a-Si:H) material and microcrystalline silicon (μc-Si) materials. Preliminary p-i-n type solar cells have led to a conversion efficiency of >8.5%. The filament is found to be rugged and remains intact even after deposition of ∼500 μm in thickness. This is in contrast to the use of conventional filament materials, such as W or Ta, whose longevity is limited to less than a few microns of deposition. Unlike the case of a Ta filament, the deposition rate remains constant with the use of a graphite filament. © 2001 American Vacuum Society.
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81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology

Influence of ion stimulated gas desorption from residual gas analyzer on partial pressure measurement

Satoshi Kurokouchi and Shigeki Kato

J. Vac. Sci. Technol. A 19, 2820 (2001); http://dx.doi.org/10.1116/1.1407241 (6 pages) | Cited 1 time

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The influence of ion stimulated gas desorption (ISD) from the ion-extraction plate of a residual gas analyzer (RGA) ion source on partial pressure measurement was evaluated, using a modified RGA. ISD from the extraction plate occurs due to bombardment with ionized gas molecules, and is thought to be closely related to physical sputtering and chemical reactions on the plate surface. Our experimental results indicate that partial pressure detection limits deteriorate due to an ISD signal increase, which in turn is dependent on total pressure, the species and kinetic energy of the ion, and the temperature of the ion-extraction plate. Where the ion-extraction plate is heated to 250 °C and the dominant gas species is massive or reactive, ISD signals account for an amount on the order of 100 ppm of partial pressure signal intensity. This ISD problem can affect the accuracy of partial pressure measurement in all pressure ranges. However, there are several methods to reduce ISD. Among the possible methods, a simple modification of the ion source to restrict the ion-bombarded area would diminish ISD the most effectively. © 2001 American Vacuum Society.
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68.43.Mn Adsorption kinetics
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Sound velocity and Young’s modulus in plasma deposited amorphous hydrogenated carbon

R. O. Dillon, Abbas Ali, N. J. Ianno, A. Ahmad, and T. Furtak

J. Vac. Sci. Technol. A 19, 2826 (2001); http://dx.doi.org/10.1116/1.1407242 (5 pages) | Cited 4 times

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The first carbon-film sound velocities obtained with the piezoelectric method are given. The a-C:H films were deposited from methane using rf plasma chemical vapor deposition at different substrate biases and thus contain varying hydrogen concentrations. Measurements of density allowed the Young’s modulii of the films to be calculated. Both the sound velocity and the Young’s modulus reached a maximum as the substrate bias changed from −47 to −175 V. The film with the maximal properties occurred at a bias of −76 V and had a sound velocity of 16.4 km/s, a Young’s modulus of 589 GPa, an optical gap of 2.16 eV and a density of 2.19 g/cm3. Although the modulus is 52% that of the directionally averaged value of diamond, it produced a sound velocity 91% that of diamond due to the lower film density. The film densities were in the range of 1.81–2.43 g/cm3 with the densest films occurring at the highest bias magnitudes. Optical gap measurements were taken with a photospectrometer and yielded a gap that decreased from 3.86 to 1.40 eV with increasing bias magnitude and thus decreasing hydrogen content. These values indicated sp3 concentrations that increased with the gap from 43% to 94% and these were consistent with Raman spectroscopy results. © 2001 American Vacuum Society.
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81.05.U- Carbon/carbon-based materials
68.60.Bs Mechanical and acoustical properties
62.65.+k Acoustical properties of solids
62.20.D- Elasticity
61.43.Er Other amorphous solids
81.40.Jj Elasticity and anelasticity, stress-strain relations
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Jg Amorphous semiconductors; glasses

Study on the characteristics of TiAlN thin film deposited by atomic layer deposition method

Jaehyoung Koo, June-Woo Lee, Taehan Doh, Yangdo Kim, Young-Do Kim, and Hyeongtag Jeon

J. Vac. Sci. Technol. A 19, 2831 (2001); http://dx.doi.org/10.1116/1.1409375 (4 pages) | Cited 6 times

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The microstructural characteristics and electrical and chemical properties of TiAlN films deposited by the atomic layer deposition (ALD) method were investigated. The growth rate of TiAlN film was measured to be 1.67 Å/cycle. TiAlN film deposited by ALD has a B1(NaCl) structure with a lattice parameter of 4.20 Å. The chlorine content in TiAlN film was below the detection limit of Auger electron spectroscopy. TiAlN film showed the columnar structure with a resistivity of about 400 μΩ cm. The sheet resistance increased abruptly after annealing at 650 °C due to the formation of a high resistivity Cu-silicide phase at the interface between the TiAlN and Si substrate. The failure of the ALD TiAlN barrier layer was observed by an etch-pit test after annealing at 600 °C for 1 h. TiAlN films deposited by the ALD method exhibited excellent film properties and improved barrier characteristics compared to other chemical vapor deposition methods. © 2001 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Ls Metallization, contacts, interconnects; device isolation
68.55.A- Nucleation and growth
61.72.-y Defects and impurities in crystals; microstructure
81.40.Gh Other heat and thermomechanical treatments
81.65.Cf Surface cleaning, etching, patterning
68.55.-a Thin film structure and morphology

Deposition of diamond films at low pressure in a planar large-area microwave surface wave plasma source

W. Y. Yeh, J. Hwang, T. J. Wu, W. J. Guan, C. S. Kou, and H. Chang

J. Vac. Sci. Technol. A 19, 2835 (2001); http://dx.doi.org/10.1116/1.1409378 (5 pages) | Cited 1 time

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In this study a planar large-area microwave plasma source is used to grow diamond films at low gas pressure. This plasma source is based on the excitation of plasma surface waves so that overdense plasmas can be generated. Above all, this plasma source is easy to scale up. For admixture of CH4/H2 gas, radical information and characteristics of the plasma are carefully characterized at low pressure. Some features different from those at high pressure are observed. A three-step process for diamond growth in the planar microwave plasma chemical vapor deposition system has been developed. High nucleation density can be achieved as a result. At a low pressure of 0.2 Torr, diamond films can be successfully deposited on a 4-in. Si(100) wafer, exhibiting a large amount of non-sp3 bonding. The effects of plasma properties on the diamond film are addressed. © 2001 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Cy Elemental semiconductors
81.05.U- Carbon/carbon-based materials
52.77.Dq Plasma-based ion implantation and deposition
68.55.-a Thin film structure and morphology
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.33.Ya Chemistry of MOCVD and other vapor deposition methods

Initial growth step and annealing effect of Ta2O5 formed by anodization of Ta foil in an ammonium tartrate electrolyte

Kwang-Soon Ahn and Yung-Eun Sung

J. Vac. Sci. Technol. A 19, 2840 (2001); http://dx.doi.org/10.1116/1.1409377 (6 pages) | Cited 5 times

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The initial growth step during the anodization of a Ta foil and structural changes in the Ta2O5 film with anodizing time and annealing temperature were investigated using cyclic voltammetry, chronoamperometry, ac impedance spectroscopy, atomic force microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Under the conditions used here, the Ta2O5 film was anodized by the island growth mechanism and the initial growth step of Ta2O5 formation is via the tunneling mode, which is thickness dependent, that is, changing from direct tunneling to defect-enhanced tunneling as the thickness is increased up to a considerable thickness (about 200 Å). The anodized Ta2O5/Ta samples were annealed by rapid thermal annealing (RTA) and Pt metals were then sputtered to produce the Pt/Ta2O5/Ta structure. Based on the leakage current versus voltage data for Pt/Ta2O5/Ta, we conclude that an anodized Ta2O5 film can be used as an insulating material for storage capacitors in combination with an optimum RTA treatment. © 2001 American Vacuum Society.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.65.-b Surface treatments
82.45.Mp Thin layers, films, monolayers, membranes
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.55.A- Nucleation and growth
82.80.Fk Electrochemical methods
68.37.Ps Atomic force microscopy (AFM)
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Dp Adsorbed layers and thin films
81.40.Gh Other heat and thermomechanical treatments
73.40.Rw Metal-insulator-metal structures

A new look at the steel cord–rubber adhesive interphase by chemical depth profiling

G. E. Hammer

J. Vac. Sci. Technol. A 19, 2846 (2001); http://dx.doi.org/10.1116/1.1410945 (5 pages) | Cited 6 times

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The adhesive interphase formed between brass plated steel cord and sulfur crosslinked rubber is known to be a complex layer of metal oxides, sulfides, and rubber. Hostile aging of this system produces changes in the structure, morphology, thickness, and mechanical properties of this layer. In a previous publication it has been shown that the overall thickness of the sulfide layer as measured by depth profiling with Auger electron spectroscopy could be used to characterize the degradation of the adhesive bond [G. E. Hammer et al., J. Vac. Sci. Technol. A 12, 2388 (1994)]. In this work multivariate statistical analysis of the sulfur Auger electron spectra was used to produce chemical depth profiles of the individual copper and zinc sulfide layers. These chemical depth profiles give new insight into the adhesion degradation mechanism on the nanometer scale. Particularly, the percentage of copper sulfide in the layer was found to be an accurate predictor of adhesion degradation. © 2001 American Vacuum Society.
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68.35.Np Adhesion
82.35.Gh Polymers on surfaces; adhesion
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.05.Bx Metals, semimetals, and alloys
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
79.20.Fv Electron impact: Auger emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
02.70.Rr General statistical methods
02.50.-r Probability theory, stochastic processes, and statistics
68.35.Ct Interface structure and roughness
68.60.Bs Mechanical and acoustical properties

Ion kinetic energy control in dual plasma deposition of thin films

L. P. Wang, B. Y. Tang, K. Y. Gan, X. B. Tian, and P. K. Chu

J. Vac. Sci. Technol. A 19, 2851 (2001); http://dx.doi.org/10.1116/1.1410947 (5 pages) | Cited 1 time

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Dual plasma deposition based on plasma immersion ion implantation and plasma deposition is a fledgling technique for the fabrication of functional thin films. One of its advantages is the easy adjustment of the ion kinetic energy during the process. It is straightforward to control the ion kinetic energy during the fabrication of conducting thin films on conducting substrates by simply varying the negative dc voltage applied to the targets. However, for the fabrication of insulating thin films or film deposition on insulating substrates, charge accumulation makes it difficult for ions to attain the proper kinetic energy. In these cases, a pulse or ac voltage is commonly employed. In this article, we theoretically investigate the process window in dual plasma deposition with respect to the pulse width and frequency of the applied voltage to avoid electrical breakdown of the film as well as large ion kinetic energy deviation. The model can deal with the deposition of insulating thin films on conducting or insulating substrates. © 2001 American Vacuum Society.
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52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Studies of mid-frequency pulsed dc biasing

P. J. Kelly, R. Hall, J. O’Brien, J. W. Bradley, P. Henderson, G. Roche, and R. D. Arnell

J. Vac. Sci. Technol. A 19, 2856 (2001); http://dx.doi.org/10.1116/1.1410949 (10 pages) | Cited 8 times

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The application of mid-frequency (100–350 kHz) pulsed dc power at the substrate is a recent development in the magnetron sputtering field. It has been found that, unlike the dc case, if the bias is pulsed in this range, the current drawn at the substrate does not saturate, but continues to increase with increasing bias voltage. In addition, this effect becomes more marked as the pulse frequency is increased. For example, under a particular set of operating conditions, a threefold increase in ion current was observed at a bias voltage of −300 V when the bias was pulsed at 350 kHz, compared to the dc case. This phenomenon is believed to be due to the initiation of a second discharge at the substrate. Pulsing the substrate bias voltage, therefore, offers a novel means of controlling the ion current drawn at the substrate. Clearly, this has significant implications in relation to film growth, sputter cleaning, and substrate preheating processes. Consequently, the variation in ion current with pulse frequency and bias voltage has been studied for an unbalanced magnetron sputtering system. In addition, substrate heating rates, current–voltage wave forms and plasma characteristics have also been investigated. A series of TiO2 and TiN films were then grown under different bias conditions. Analysis of these films showed that the application of pulsed dc power at the substrate can significantly influence film structure and properties. In particular, shifts in crystalline structure and texture were observed. © 2001 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

Dynamics and thermal stability of Cs superstructures on a Pt(111) surface

Takahiro Kondo, Hiroyuki Kozakai, Takashi Sasaki, and Shigehiko Yamamoto

J. Vac. Sci. Technol. A 19, 2866 (2001); http://dx.doi.org/10.1116/1.1410946 (4 pages) | Cited 7 times

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Utilizing thermal energy helium atom scattering we have made clear the dynamics from formation to destruction and the thermal stability of the Cs superstructures on a Pt(111) surface. Among three structures identified by low energy electron diffraction, both the (math×math) and the (math×math)R30° structures are unstable and are destroyed at around 350 K, and transform into the (2×2) structure. The (2×2) structure which is stable up to 450 K, exhibits large corrugation amplitudes of the potential energy surface. This suggests a strong bond between Cs and Pt atoms and the localization of electron charge distribution as a result of the charge transfer from Cs atoms to the substrate Pt(111) surface. It is also suggested that the work function minimum is closely related to this charge transfer of Cs atoms forming the (2×2) structure. © 2001 American Vacuum Society.
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68.43.Fg Adsorbate structure (binding sites, geometry)
81.05.Bx Metals, semimetals, and alloys
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.60.Dv Thermal stability; thermal effects
68.43.Mn Adsorption kinetics
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
73.30.+y Surface double layers, Schottky barriers, and work functions
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena

Structural and optical properties of thin lead oxide films produced by reactive direct current magnetron sputtering

S. Venkataraj, Jean Geurts, Hansjörg Weis, Oliver Kappertz, Walter K. Njoroge, R. Jayavel, and Matthias Wuttig

J. Vac. Sci. Technol. A 19, 2870 (2001); http://dx.doi.org/10.1116/1.1410948 (9 pages) | Cited 11 times

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The structural and optical properties of thin lead oxide films were studied. Thin films were prepared by reactive dc magnetron sputtering of lead (Pb) targets in an Ar/O2 mixture. The structure has been determined by x-ray diffraction measurements, which show that crystalline lead oxide films of different composition (PbO, PbO1.44, Pb2O3, and PbO2) have been formed upon increasing oxygen flow (partial pressure). This result is confirmed by Raman spectroscopy. The effect of postdeposition annealing on the structural properties of PbO films reveals that the film structure is governed by both energetics and kinetics. X-ray reflectivity measurements were used to determine the thickness, density, and roughness of the films. The calculated film density values are almost equal to the bulk density of the material, showing that compact, nearly void free films are formed. The optical properties of the films have been studied from the reflectance and transmittance spectra recorded by optical spectroscopy measurements from 10 000 (1.24 eV) to 50 000 (6.21 eV) cm−1. From these data we have determined optical properties such as the dielectric function, the optical band gap Eg and the refractive index n as well as the film thickness. © 2001 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
78.66.Nk Insulators
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.66.Fn Inorganic compounds

Fabrication and characterization of C implantation standards for Si1−x−yGexCy alloys

T. Laursen, D. Chandrasekhar, R. L. Hervig, J. W. Mayer, David J. Smith, and C. Jasper

J. Vac. Sci. Technol. A 19, 2879 (2001); http://dx.doi.org/10.1116/1.1412652 (5 pages) | Cited 1 time

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Known amounts of carbon were implanted into a set of Si1−xGex alloy films (0<x<0.35) to provide quantification standards for C composition measurements of Si1−x−yGexCy alloys by secondary ion mass spectrometry. The implanted doses were fixed to within ±2%, the thicknesses of implanted films were measured to within ±1% using high-resolution electron microscopy, and the Ge concentrations were determined to within ±0.5% using Rutherford backscattering spectroscopy. For Si:Ge ratios in the range Si66Ge34 to Si91Ge9, the relative sensitivity factor for carbon with respect to silicon, and for carbon relative to germanium, both decreased substantially with increasing Ge content. © 2001 American Vacuum Society.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
06.20.F- Units and standards
61.72.up Other materials
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Micromachined piezoresistive cantilever array with integrated resistive microheater for calorimetry and mass detection

N. Abedinov, P. Grabiec, T. Gotszalk, Tz. Ivanov, J. Voigt, and I. W. Rangelow

J. Vac. Sci. Technol. A 19, 2884 (2001); http://dx.doi.org/10.1116/1.1412654 (5 pages) | Cited 20 times

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We describe a microcantilever calorimeter consisting of an array of ten cantilevers. Each single cantilever is capable of detecting heat energy with the resolution of 50 nW Hz(−0.5). The device is based on a Si microcantilever coated with a 1 μm thick layer of SiO2 deposited with a 700 nm thick layer of aluminum which forms a resistive microheater. Heat fluxes are monitored by detecting the cantilever deflection (bending) due to the bimaterial structure of the cantilever (dissimilar thermal expansion properties of SiO2 and Al). The resistive microheater serves for calibration of the heat flux and for temperature sensing. In our design a piezoresistive Wheatstone bridge detector is applied for measurements of the cantilever beam deflection. The cantilever displacement detection system enables investigations in ultrahigh vacuum and low temperature conditions. The microcantilevers are manufactured in a one-dimensional array having ten individual microcantilevers which is the first step in the fabrication of an infrared detector array with spatial resolution. The displacement sensitivity versus temperature change of the described sensor array as a function of temperature change is of about 2 nm/K and an estimated resolution limit of temperature detection is ≈10−3 K at 300 K. In order to demonstrate the cantilever bending sensitivity we employ the piezoresistive cantilever array as a picogram microbalance. © 2001 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
06.30.Dr Mass and density
06.20.F- Units and standards
07.10.Cm Micromechanical devices and systems
07.20.Fw Calorimeters
07.20.Dt Thermometers

Steady-state direct-current plasma immersion ion implantation using a multipolar magnetic field electron cyclotron resonance plasma source

Xuchu Zeng, Honghui Tong, Ricky King-Yu Fu, Paul K. Chu, Zejin Xu, and Qingchuan Chen

J. Vac. Sci. Technol. A 19, 2889 (2001); http://dx.doi.org/10.1116/1.1412653 (4 pages) | Cited 4 times

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In semiconductor plasma immersion ion implantation (PIII) applications such as the synthesis of silicon-on-insulator by hydrogen PIII and ion cut, only ions arriving at the top surface of the sample stage are important. The ions implanted into the other surfaces of the sample chuck actually not only decrease the efficiency of the power supply and plasma source but also give rise to metallic contamination. In addition, low energy ions introduced by the initial plasma sheath propagation, pulse rise time, and pulse fall time introduce a large surface hydrogen concentration that creates surface damage and affects the wafer bonding efficacy. We have theoretically demonstrated direct-current PIII (DC-PIII) which retains the x–y immersion characteristic while simultaneously reducing this low energy ion component, obviating the need for the expensive power modulator, and extending the voltage ceiling that is no longer limited by the vacuum chamber and power modulator. In this article, we describe our hydrogen DC-PIII experiments using a conducting grid placed between the wafer stage and a multipolar electron cyclotron resonance plasma source. The grounded grid stops the propagation of the plasma sheath, thereby removing the vacuum chamber size limitation. Ions are formed in the plasma sustained by an external plasma source above the grid and accelerated through the lower zone to be implanted into the wafer biased by only a dc power supply. Atomic force microscopy, hydrogen forward scattering, and secondary ion mass spectrometry analyses indicate uniform hydrogen PIII into a 100 mm silicon wafer and the surface hydrogen component is indeed reduced significantly compared to conventional pulsed PIII. © 2001 American Vacuum Society.
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52.77.Dq Plasma-based ion implantation and deposition
61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
68.37.Ps Atomic force microscopy (AFM)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Wall-dependent etching characteristics of organic antireflection coating in O2+halogen/hydrogen halide plasma

Songlin Xu, Thorsten Lill, and Dragan Podlesnik

J. Vac. Sci. Technol. A 19, 2893 (2001); http://dx.doi.org/10.1116/1.1412655 (7 pages) | Cited 9 times

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Process instability in plasma etching of organic bottom-antireflection coating (BARC) using the plasma of O2 mixed with halogen (Cl2) or hydrogen halide (HBr, HCl) has been studied. From a series of process tests performed on a high density plasma etcher, the process instability has been found to be chamber-wall related as the BARC etch rate and critical-dimension bias shift when chamber coating changes. The process sensitivity to the chamber wall condition depends on the type of halogen-containing additive used and the O2 percentage in the total gas feed. Through plasma diagnostics, the root cause of the process shift has been identified as the variation in the surface recombination rate of reactive free radicals with chamber wall condition. The recombination of O radicals to form O2 is faster on alumina/anodized aluminum than on silicon oxide so that the O radical density becomes lower in the bulk plasma. The enhanced competing surface recombination of O and H radicals when HBr or HCl is used further lowers the O density, leading to a more significant process shift. Approaches to improve the process stability and performance consistency have been discussed. © 2001 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Analytic expressions of the speed factor for turbomolecular pumps

Yu-Wen Chang and Rong-Yuan Jou

J. Vac. Sci. Technol. A 19, 2900 (2001); http://dx.doi.org/10.1116/1.1414123 (5 pages)

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Since Kruger developed the theory for a single stage of a turbomolecular pump in 1960, it has been widely applied to the design and research of turbomolecular pumps for the past 30 years. One of the main ideas in his theory is that the maximum pressure ratio can be expressed as the ratio of the transmission probabilities of the molecules that pass through the blade row upstream to downstream to one of downstream to upstream, and that the maximum speed factor can be expressed as the difference between the above two transmission probabilities. Considering that Kruger's theory was derived under zero flow, we construct a modified expression for the maximum speed factor in this article. In addition, a second approximate expression for the case where the gas flow is between the maximum pressure ratio and maximum speed factor is proposed. The two new expressions are both verified using the direct simulation Monte Carlo method and show a good match. © 2001 American Vacuum Society.
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07.30.Cy Vacuum pumps
02.70.Uu Applications of Monte Carlo methods

Effect of substrate–film lattice mismatch in La0.7Ba0.3MnO3−δ thin films for transport properties

K. Hayashi, E. Ohta, and H. Wada

J. Vac. Sci. Technol. A 19, 2905 (2001); http://dx.doi.org/10.1116/1.1414124 (5 pages) | Cited 2 times

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In this study, we explore the use of La0.7Ba0.3MnO3−δ (LBMO) for use in uncooled infrared bolometers. To obtain a high temperature coefficient of resistance (TCR) (defined as 1/R dR/dT) at near-room temperature, thin films were deposited on SrTiO3 (100), LaAlO3 (100) and MgO (100) substrates by a laser ablation method. The substrate–film lattice mismatch between these substrates and LBMO films caused misfit stress which changed the surface structure of the films and influenced their temperature dependence of resistivity. The microstructures of films were characterized by x-ray diffraction and atomic force microscope. As a result, the LBMO film deposited on SrTiO3 (the LBMO/STO film) had crystallinity like LBMO bulk and showed high orientation of the substrate. And its temperature dependence of resistivity agreed with LBMO bulk. Near 300 K the LBMO/STO film showed high TCR values, about 4%/K. In addition, the TCR values of the LBMO/STO films were over 2%/K over a wide temperature range centered near 300 K. These results suggest that LBMO/STO films are possible for use as an uncooled infrared bolometer material. © 2001 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
75.47.De Giant magnetoresistance
68.37.Ps Atomic force microscopy (AFM)
75.47.Gk Colossal magnetoresistance
71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions

Real-time/in situ diffraction study of phase and microstructural evolution in sputtered β-Ta/Ta2O5 films

J. F. Whitacre, S. M. Yalisove, and J. C. Bilello

J. Vac. Sci. Technol. A 19, 2910 (2001); http://dx.doi.org/10.1116/1.1414119 (10 pages)

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The evolution of texture, grain size, and phase content in sputtered β-Ta/Ta2O5 films was studied and controlled in situ using a laboratory-based real-time x-ray diffraction system. The films were dc magnetron sputter deposited using sputter gas (Ar) pressures ranging from 2 to 20 mTorr. To collect diffraction data during growth, a grazing incidence x-ray scattering (GIXS) configuration was necessary. Because this configuration complicated the interpretation of texturing data, complete Schultz geometry pole figures were also used to characterize the films after growth, and the relationship between pole figure and GIXS data was examined. The film composition was evaluated using sputter profile x-ray photoelectron spectroscopy and secondary ion mass spectroscopy. It was found that the degree and rate of (002) out-of-plane texturing was systematically stronger in films grown at lower Ar pressures (< 10 mTorr). These films were predominantly β-Ta in composition and had relatively large grains (∼50 nm in diameter). Films grown using progressively higher Ar pressures had increasing amounts of Ta2O5, developed a (002) out-of-plane texture more slowly, and were nanocrystalline/amorphous in nature. Data from depositions where the Ar pressure was changed during growth showed that the deposition environment at the instant of layer formation determined the phase content, degree of texture, and grain size in the developing film; the characteristics of previous layers had little bearing on subsequent growth. This shows that tailored multilayer β-Ta/Ta2O5 films may be created and monitored in situ. © 2001 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.-y Defects and impurities in crystals; microstructure
79.60.Dp Adsorbed layers and thin films
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Diamond-based composite layers as protective coatings for ion beam extraction systems

M. L. Terranova, V. Sessa, S. Piccirillo, M. Rossi, S. Valeri, and M. Materassi

J. Vac. Sci. Technol. A 19, 2920 (2001); http://dx.doi.org/10.1116/1.1414121 (5 pages) | Cited 1 time

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W-containing polycrystalline diamond films were produced by a hybrid chemical vapor deposition- powder flowing technique, in order to test the feasibility of using composite diamond-based materials as protective coatings for acceleration grids subjected to ion bombardment. The morphology and structure of the composite layers, deposited on Mo substrates, were investigated by scanning electron microscopy and reflection high-energy electron diffraction. It is found that W insertion substantially lowers the resistivity of the diamond-based layers (around 10−2Ω cm) but does not modify the lattice parameters of the host diamond matrix. The performance of such coatings for shielding Mo grids from ion-induced sputtering was tested using 1 keV Ar+ beams. The Auger electron spectroscopy spectra indicated that the dose of 6×1019 ions/cm2 employed was not sufficient for complete erosion of the composite layers, for which sputtering yields in the range of 0.6–0.9 atoms/ion were measured. The secondary electron emission induced by 1.5–4.0 keV Ar+ ions was investigated and compared with the emission from uncoated Mo samples. © 2001 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.-b Surface treatments
81.05.U- Carbon/carbon-based materials
81.05.Cy Elemental semiconductors
62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Fv Electron impact: Auger emission
29.25.-t Particle sources and targets
07.77.Ka Charged-particle beam sources and detectors

Influence of the elemental composition and crystal structure on the vacuum properties of Ti–Zr–V nonevaporable getter films

C. Benvenuti, P. Chiggiato, A. Mongelluzzo, A. Prodromides, V. Ruzinov, C. Scheuerlein, M. Taborelli, and F. Lévy

J. Vac. Sci. Technol. A 19, 2925 (2001); http://dx.doi.org/10.1116/1.1414122 (6 pages) | Cited 9 times

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Nonevaporable thin film getters based on the elements of the fourth and fifth columns of the periodic table were deposited by sputtering. Among the some 20 alloys studied to date, the lowest activation temperature (about 180 °C for a 24 h heating) was found in the Ti–Zr–V system with a well-defined composition range. Characterization of the activation behavior of such Ti–Zr–V films is presented. The evolution of the surface chemical composition during activation is monitored by Auger electron spectroscopy and the functional properties are evaluated by pumping speed measurements. The pumping speed characteristics are quite similar to those already measured for commercially available nonevaporable getter materials, except for the much lower saturation coverage for CO. This inconvenience, which is due to the smooth surface structure of these films, can be counteracted by increasing the roughness of the substrate. © 2001 American Vacuum Society.
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68.55.Nq Composition and phase identification
79.20.Fv Electron impact: Auger emission
07.30.Cy Vacuum pumps
61.66.Dk Alloys
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.-d Microscopy of surfaces, interfaces, and thin films

Photocatalytic, antifogging mirror

K. Takagi, T. Makimoto, H. Hiraiwa, and T. Negishi

J. Vac. Sci. Technol. A 19, 2931 (2001); http://dx.doi.org/10.1116/1.1415357 (5 pages) | Cited 22 times

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This article is about the coating of thin titanium dioxide film by sputter deposition. When irradiated with solar light, thin titanium dioxide film exhibits high oxidizing power and provides sterilizing, cleaning, decomposing, and hydrophylic effects. This technique has already been used for coating building walls by the sol–gel method and by others and has been partly commercialized to make automotive sideview mirrors. There have been no practical applications of the sputter deposition method so far, but establishment of the coating method is expected because of its excellent properties of film production techniques such as film thickness uniformity, film quality durability, and freedom from environmental pollution. In this article we discuss the establishment of the method of evaluating the quality of thin titanium dioxide film, establishment of sputter-deposition conditions, and the results of observation by x-ray diffraction and atomic force microscopy of the thin film. It was found that titanium dioxide films, 200 nm or more in thickness, have the above mentioned performance and that sputter deposition allows the film to form without heating. © 2001 American Vacuum Society.
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68.55.-a Thin film structure and morphology
78.66.Nk Insulators
81.15.Cd Deposition by sputtering
42.79.Wc Optical coatings
82.50.-m Photochemistry
42.79.Bh Lenses, prisms and mirrors

Application of magnetic neutral loop discharge plasma in deep silica etching

W. Chen, K. Sugita, Y. Morikawa, S. Yasunami, T. Hayashi, and T. Uchida

J. Vac. Sci. Technol. A 19, 2936 (2001); http://dx.doi.org/10.1116/1.1415355 (5 pages) | Cited 7 times

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The electron temperature Te is one of the key parameters for process plasma because the decomposition of most reactive gases depends on the kinetic energy of electrons in the plasma. Pressure is another important parameter in the etching process for microelectromechanical systems (MEMS). Low pressure can avoid etch product substrate redepositing by reducing the collision between neutral particles and etch products in the gas phase. Also, low pressure may reduce the scattering of incident ions in the sheath that may reduce the negative taper angle for trench etching. Therefore, this study is focused on low pressure (<0.67 Pa), low Te plasma production for optical MEMS etching processes. To reduce the Te and keep the high density of the plasma, use of a parallel turn antenna was proposed and it was applied in magnetic neutral loop discharge plasma, where the Te is desirably reduced to about 2.5 eV while the density is about 1.2×1011 cm−3 at pressure of 0.2 Pa. With this improvement in plasma production, fused quartz and chemical vapor deposition SiO2 were successfully etched in a trench 5–40 μm deep at a high etch rate of over 500 nm/min. The vertical angles are about 90° and the surface roughness is less than 50 nm as evaluated by a scanning electron microscope picture, where Cr, WSi and Si were used as hard masks of SiO2 in order to achieve the selectivity required. © 2001 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
52.50.-b Plasma production and heating
52.80.Dy Low-field and Townsend discharges
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
68.35.B- Structure of clean surfaces (and surface reconstruction)

Reaction of gas-phase atomic hydrogen with NO on Ru(001)

Tae Won Kim, Michael J. Weiss, Chrisopher J. Hagedorn, and W. Henry Weinberg

J. Vac. Sci. Technol. A 19, 2941 (2001); http://dx.doi.org/10.1116/1.1415358 (5 pages) | Cited 7 times

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The reactions of gas-phase atomic hydrogen [H(g)] and deuterium [D(g)] with preadsorbed nitric oxide [NO(a)] on the hexagonally close-packed Ru(001) surface have been studied by means of temperature-programmed desorption and high-resolution electron energy loss spectroscopy (HREELS). Exposure of gas-phase atomic deuterium to the saturated NO overlayer at a surface temperature of 100 K results in the observation of N2O, D2O, D2, NO, N2, and O2 in subsequent thermal desorption spectra. Since D2O is formed at low surface temperatures, an Eley–Rideal-like mechanism in which deuterium atoms from the gas phase react with the oxygen end of the preadsorbed NO is suggested. Spectroscopic evidence for this reaction on the Ru(001) surface is provided by HREEL spectra which show vibrations at 983 cm−1 [after H(g) exposure] and 977 cm−1 [after D(g)]. Since the loss at 983 cm−1 has not shifted significantly upon deuterium substitution, these losses are assigned to weakened N–O stretches of NOH (NOD) species. These species are stable after annealing to 200 K on Ru(001). © 2001 American Vacuum Society.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.Mn Adsorption kinetics
79.20.Uv Electron energy loss spectroscopy
68.35.Ja Surface and interface dynamics and vibrations

Gas-phase studies in inductively coupled fluorocarbon plasmas

M. Schaepkens, I. Martini, E. A. Sanjuan, X. Li, G. S. Oehrlein, W. L. Perry, and H. M. Anderson

J. Vac. Sci. Technol. A 19, 2946 (2001); http://dx.doi.org/10.1116/1.1415361 (12 pages) | Cited 19 times

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Quantitative results from infrared laser absorption spectroscopy (IRLAS) of CF and CF2 radicals and COF2 products in inductively coupled plasmas fed with C2F6, CHF3 and C4F8 are presented and compared with results simultaneously obtained by mass spectrometry and optical emission spectroscopy. These plasma gas-phase analysis results are discussed and compared to fluorocarbon deposition and etching rates resulting from plasma–surface interactions at the substrate. It is found that COF2 species are being formed (1) during O2 plasma cleaning of a fluorocarbon contaminated reactor and (2) during SiO2 etching in fluorocarbon plasmas, which in this work occurred at the quartz coupling window as a result of capacitive coupling between the induction coil and the plasma. IRLAS results on CF and CF2 densities are compared to fluorocarbon deposition and etching rates and it is found that low CF and/ or CF2 density does not necessarily translate into a low fluorocarbon deposition rate. A relatively high deposition rate can be achieved at conditions with a high ion current density and low CF and CF2 densities. © 2001 American Vacuum Society.
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52.50.Dg Plasma sources
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.77.Dq Plasma-based ion implantation and deposition
52.77.Bn Etching and cleaning
52.70.Nc Particle measurements
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.65.Cf Surface cleaning, etching, patterning
52.25.-b Plasma properties

Inner surface coating of TiN by the grid-enhanced plasma source ion implantation technique

Bin Liu, Guling Zhang, Dajung Cheng, Chizi Liu, Rui He, and Si-Ze Yang

J. Vac. Sci. Technol. A 19, 2958 (2001); http://dx.doi.org/10.1116/1.1415356 (5 pages) | Cited 12 times

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An inner surface coating of a tubular sample was realized by a new method of grid-enhanced plasma source ion implantation (GEPSII), which is an extension of previous plasma source ion implantation inner surface modification. In GEPSII, a rf plasma core is produced between a center cathode and a grid electrode, which are coaxially arranged inside the tubular sample. Negative high voltage pulses are applied between the grid electrode and the inner surface of the tubular sample, thus an accelerating field for positive ions can be established between the grid electrode and the inner surface of the sample. In addition, particles of solid matter can be introduced into the rf plasma by sputtering the cathode, thus, it is possible to realize metal ion implantation and film deposition. In this article, the concept of GEPSII and some preliminary measurement results of this method are presented, and TiN films are produced on the inner surface of a tubular sample, which is a cylinder of an automobile. The plasma density profiles and plasma electron temperature inside the sample are measured by a Langmuir probe. It is shown that the axial plasma density profile is rather uniform in GEPSII. TiN films were also deposited on single-crystal silicon substrates, which are arranged on the inner surface of the cylinder. © 2001 American Vacuum Society.
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52.77.Dq Plasma-based ion implantation and deposition
61.72.up Other materials
61.82.Ms Insulators
52.70.Ds Electric and magnetic measurements
61.80.Jh Ion radiation effects

Characteristics of a taper-seal type gasket for the Conflat® sealing system

Satoshi Kurokouchi, Shinsaku Morita, and Masayuki Okabe

J. Vac. Sci. Technol. A 19, 2963 (2001); http://dx.doi.org/10.1116/1.1415359 (5 pages) | Cited 2 times

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Disk (flat ring) gaskets are commonly employed in conjunction with the ConFlat® metal sealing system. The use of the disk gasket, however, limits the seal performance on the ConFlat system because considerable tightening force is wasted in the sealing process when the flange knife edge cleaves the surfaces of the disk gasket. The taper-seal type gasket, which seals entirely by the compression of its corners without surface shearing, can be expected to improve the inefficiency of the ConFlat system relative to performance using conventional disk gaskets. Tightening tests on both gasket versions demonstrated that the seal area on the taper-seal type gasket was some 1.6–3.7 times larger than that on conventional disk gaskets, even when the taper-seal type gasket material is relatively hard. This result suggests that the tightening force acts more effectively to form a sealed area on a taper-seal gasket than a disk gasket. The two types of gaskets also differed in their stress distributions under the tightening load. Results of stress analyses using computer simulation showed that the stress concentration occurred in the conventional disk gasket around the tip of flange knife edge, and that maximum stress could be over four times larger than that seen in the taper-seal gasket. This excessively high stress in the disk gasket prevented achievement of a wide seal area, and intensified the creep of gasket materials during the baking process, this increasing the probability of leaks developing. The characteristic mode of deformation of the taper-seal gasket generates a highly stable stress distribution, virtually independent of the tightening torque; thus, good seal performance is realized, even under sever thermal cycling conditions. © 2001 American Vacuum Society.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Investigation of diamond film deposition on steel without and with ion beam nitriding pretreatment

N. G. Shang, C. H. Lee, X. T. Zhou, F. Y. Meng, C. Y. Chan, S. T. Lee, and I. Bello

J. Vac. Sci. Technol. A 19, 2968 (2001); http://dx.doi.org/10.1116/1.1415360 (6 pages) | Cited 1 time

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The surface morphology, film quality, interface structure, growth rate and adhesion of diamond films prepared by hot filament chemical vapor deposition on commercial steel substrates with and without ion beam nitriding pretreatment were investigated by scanning electron microscopy, x-ray diffraction, scanning Auger spectroscopy, a Vickers microindenter, and microRaman spectroscopy. Apart from quite different surface morphologies, both the quality and growth rate of diamond films deposited on the ion beam nitrided steel substrates were higher than those on the unnitrided steel substrates. Similar diamond/steel interface structure were observed on both the nitrided and unnitrided steel. Diamond films were grown on steel substrates via carbide interlayers formed in situ during the diamond deposition rather than via a graphitic soot interlayer. Ion beam nitriding appeared to enhance the diamond growth through thickening of the carbide interlayer. The adhesion of diamond films on the nitrided steel was tested by a Vickers microindenter. © 2001 American Vacuum Society.
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81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Np Adhesion
79.20.Fv Electron impact: Auger emission
78.30.Am Elemental semiconductors and insulators
78.66.Nk Insulators
68.60.Bs Mechanical and acoustical properties
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Chemical vapor deposition of an electroplating Cu seed layer using hexafluoroacetylacetonate Cu(1,5-dimethylcyclooctadiene)

W. H. Lee, Y. K. Ko, I. J. Byun, B. S. Seo, J. G. Lee, P. J. Reucroft, J. U. Lee, and J. Y. Lee

J. Vac. Sci. Technol. A 19, 2974 (2001); http://dx.doi.org/10.1116/1.1405511 (5 pages) | Cited 8 times

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© 2001 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Bx Metals, semimetals, and alloys
73.61.At Metal and metallic alloys
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Preferential resputtering phenomenon on the surface of (100)-oriented Ni–Pt films: Effect of substrate bias during sputter deposition

J. Shi, R. Zhou, and M. Hashimoto

J. Vac. Sci. Technol. A 19, 2979 (2001); http://dx.doi.org/10.1116/1.1407243 (3 pages)

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Effects of substrate bias during sputter deposition on the structure and composition of Ni–Pt/MgO(100) films were investigated. Ni–Pt films deposited at 220 °C are composed of a Ni–Pt substitutional solid solution of face-centered cubic structure. All the films are single crystalline with identical crystallographic orientation with the substrate, regardless of the substrate bias. However, the composition of the films was significantly affected by the substrate bias: Pt content increased with increasing the substrate bias within the investigated range. This phenomenon is explained in terms of the preferential resputtering of Ni by impinging ions and neutrals generated by the substrate bias. Furthermore, the crystallinity of the films was also affected by the substrate bias. © 2001 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
61.66.Dk Alloys
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Reduction of artifacts in temperature programmed desorption measurements of field generated, real-life, powered samples

V. S. Smentkowski and A. L. Linsebigler

J. Vac. Sci. Technol. A 19, 2982 (2001); http://dx.doi.org/10.1116/1.1409376 (5 pages)

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Temperature programmed desorption (TPD) is a powerful surface analytical technique used for studies of adsorbate systems when background effects such as desorption from the mounting wires and/or the heater assembly can be minimized. Researchers often use TPD measurements to determine the desorption characteristics of field generated, real-life samples that have been prepared under ambient conditions. Since real-life samples are generated under ambient conditions, the potential for background effects is significantly enhanced. In many cases, background effects and their implications on data analysis are not considered. It will be demonstrated that background effects are very significant for real-life, field generated samples when traditional protocols are used for TPD measurements. We have devised a novel experimental protocol to reduce background effects during TPD measurements of field generated, real-life powdered samples. The novel experimental apparatus and procedures will be described. TPD spectra measured using the new protocol will be compared with spectra measured using traditional protocols. © 2001 American Vacuum Society.
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82.80.-d Chemical analysis and related physical methods of analysis
68.43.Vx Thermal desorption
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