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Mechanisms for CF₂ radical generation and loss on surfaces in fluorocarbon plasmas

Da Zhang and Mark J. Kushner

J. Vac. Sci. Technol. A 18, 2661 (2000); http://dx.doi.org/10.1116/1.1319816 (8 pages) | Cited 34 times

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During fluorocarbon plasma etching, plasma-surface reactions result in the surface acting as either a source or sink for reactive species, thereby impacting the properties of the bulk plasma. For example, experiments have shown that surfaces in radio frequency (rf) capacitively coupled discharges can be either sources or sinks of CF₂ depending on, among other properties, the sheath potential. The coupling of rf bulk and surface reactions, and their combined effects on the CF₂ density, were investigated using an integrated plasma equipment and surface kinetics model. While CF₂ sticking on surfaces led to its loss, CF₂ can be generated from surfaces by energetic ion bombardment resulting in sputtering of polymeric films, or neutralization and dissociation of ions. The net effect of a surface for CF₂ production depends on the relative rates of these loss and generation processes. A surface can transform from a net CF₂ sink at low incident ion energies to a CF₂ source at high ion energies because the CF₂ yield by ion–surface interactions typically increases with increasing ion energy. The sensitivity of the model to probabilities of major surface reactions was also investigated. © 2000 American Vacuum Society.

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52.40.Hf	Plasma-material interactions; boundary layer effects
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
81.65.Cf	Surface cleaning, etching, patterning
82.20.-w	Chemical kinetics and dynamics

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Transient plasma-induced emission analysis of laser-desorbed species during Cl₂ plasma etching of Si

Jae Young Choe, N. C. M. Fuller, Vincent M. Donnelly, and Irving P. Herman

J. Vac. Sci. Technol. A 18, 2669 (2000); http://dx.doi.org/10.1116/1.1290375 (11 pages) | Cited 8 times

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The surface during the etching of Si in a Cl₂ inductively-coupled plasma (ICP) was analyzed by laser desorption (LD), followed by detection of the desorbed species by monitoring the transient changes by plasma-induced emission (PIE). Optical emission from Si, SiCl, SiCl₂, and possibly other species was detected in situ using this LD-PIE method as a function of rf power, substrate bias, and pressure. The surface coverage of chlorine was determined by normalizing the LD-PIE signal by either of two ways: by the electron density, as measured by microwave interferometry, or by using the background PIE signal. Little change in surface coverage was observed as the ion density was changed by varying the rf power supplied to the ICP, confirming the observation made using laser-induced fluorescence (LIF) detection (LD-LIF). The LD-PIE signal is related to the density of species desorbed from the surface and subsequently excited by electrons. LD-PIE analysis of the surface is more versatile than LD-LIF—sometimes it can detect the desorbed species while LD-LIF cannot. Still, it requires calibration to account for the electron collision-induced excitation of the laser-desorbed species. © 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
81.65.Cf	Surface cleaning, etching, patterning
68.03.Fg	Evaporation and condensation of liquids
68.43.Mn	Adsorption kinetics
79.20.La	Photon- and electron-stimulated desorption
68.43.-h	Chemisorption/physisorption: adsorbates on surfaces

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Surface loss coefficients of CF_x and F radicals on stainless steel

Harmeet Singh, J. W. Coburn, and David B. Graves

J. Vac. Sci. Technol. A 18, 2680 (2000); http://dx.doi.org/10.1116/1.1308585 (5 pages) | Cited 12 times

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The surface loss coefficients of CF_x (x=1–3) and F radicals have been measured on the stainless steel walls of the differential pumping systems of a plasma reactor. This measurement is made by comparing the beam to background signal ratio of the radicals measured by appearance potential mass spectrometry. The surface loss of the radicals in the differential pumping stages of the vacuum system, in addition to the pumping of the species due to the vacuum pump, increases the beam to background signal ratio of the radical species. The measured loss coefficients are found to be lower than those reported on surfaces that have been exposed to fluorocarbon plasmas. This suggests that the loss coefficients of the species are dependent on the surface coverage of the radicals (CF_x and F), which are lower on the walls in the differential pumping system. The measured loss coefficients in the differential pumping system are an order of magnitude lower than the loss coefficients measured in the afterglow of plasma chambers reported in the literature. We suggest the difference in the loss coefficients of radicals in the plasma chamber and those measured in this work are due to the differences in surface coverage in the two cases. © 2000 American Vacuum Society.

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52.40.Hf	Plasma-material interactions; boundary layer effects
52.80.Pi	High-frequency and RF discharges
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
07.30.Cy	Vacuum pumps
82.80.Ms	Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

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Ion and substrate effects on surface reactions of CF₂ using C₂F₆, C₂F₆/H₂, and hexafluoropropylene oxide plasmas

Carmen I. Butoi, Neil M. Mackie, Keri L. Williams, Nathan E. Capps, and Ellen R. Fisher

J. Vac. Sci. Technol. A 18, 2685 (2000); http://dx.doi.org/10.1116/1.1312371 (14 pages) | Cited 30 times

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The surface reactivity of CF₂ radicals has been characterized during plasma processing of a variety of substrates using the imaging of radicals interacting with surfaces technique. The plasma molecular beam sources are 100% C₂F₆, 50/50 C₂F₆/H₂, and 100% hexafluoropropylene oxide (HFPO) gas mixtures. Simulation of spatially resolved laser-induced fluorescence images in the 100% C₂F₆ system shows that CF₂ has a scatter value, S, >1.0 with SiO₂, polyimide and photoresist substrates. A scatter of >1.0 indicates that CF₂ molecules are generated at the surface during plasma processing. With the 50/50 C₂F₆/H₂ plasma, CF₂ exhibits a lower scatter value (∼0.85) on Si, SiO₂, and polyimide substrates. With the HFPO plasma source, S⩾1 for all continuous wave powers and substrates processed. Values of S∼0.8 are obtained for ion-free and pulsed plasmas, however, revealing ion collisions with the substrate play an important role in the surface generation of CF₂. The radical-surface interaction data are correlated with data from surface characterization by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy of the substrates. The key finding is that our results suggest the surface reactivity behavior of CF₂ radicals correlates well to the overall plasma process (etching or deposition). © 2000 American Vacuum Society.

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73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
81.65.Cf	Surface cleaning, etching, patterning
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
81.15.Cd	Deposition by sputtering

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Carbon deposition by electron beam cracking of hydrocarbons on Ta₂Zn₃O₈ thin film phosphors

Caroline A. Kondoleon, Philip Rack, Eric Lambers, and Paul Holloway

J. Vac. Sci. Technol. A 18, 2699 (2000); http://dx.doi.org/10.1116/1.1319817 (7 pages) | Cited 4 times

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The cathodoluminescence (CL) brightness from thin film Ta₂Zn₃O₈ has been studied as a function of vacuum and electron dose. The thin films were prepared by sputtered deposition followed by rapid thermal annealing at 1100 °C for 1 min. Under bombardment by 2 keV electrons, the films produce a blue luminescence with a dominant wavelength of 386 nm. These films were exposed to residual vacuum gas dominated by H₂ and H₂O at pressures ranging from 10⁻⁸ to 10⁻⁶ Torr with <10% loss in CL brightness for an electron dose of 23 C/cm². However, when hydrocarbons from colloidal graphite “paint” raised the base pressure of the vacuum from 2×10⁻⁷ to 9×10⁻⁷ Torr, the CL brightness was degraded to 5% of its original value after ≈4 h at 2.7×10⁻⁴ A/cm² (corresponding to a dose of 3.9 C/cm²). Degradation stopped when the electron beam was off or could not strike the surface. Auger analysis showed a 1000-Å-thick layer of carbon from electron beam cracked hydrocarbons. The effect of electron beam cracked carbon was concluded to be absorption of luminescent photons. The hydrocarbon contaminants were removed by long term baking of the vacuum system. © 2000 American Vacuum Society.

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78.60.Hk	Cathodoluminescence, ionoluminescence
78.66.Nk	Insulators
68.55.-a	Thin film structure and morphology
61.80.Fe	Electron and positron radiation effects
61.82.Ms	Insulators

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Change in surface roughness with the thickness of TiO₂ film grown on MgO(001) by Ar-ion beam sputtering

Takeshi Uchitani and Kunisuke Maki

J. Vac. Sci. Technol. A 18, 2706 (2000); http://dx.doi.org/10.1116/1.1312375 (3 pages) | Cited 2 times

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The surface roughness, R_a, and the crystallinity are studied for the rutile-type TiO₂ films at their thickness, d, above 10 nm deposited on the air-cleaved MgO(001) held at 630 °C at 3.1×10⁻³ Pa in the partial pressure of O₂ by sputtering the Ti target by Ar-ion beam accelerated with 1.2 kV. The amount of R_a estimated by observing the surface morphology with an AFM is the order of nanometers and changes with d according to d^1/2. The linear relationship between the intensity ratio of the (110) peak for the TiO₂ to the (004) peak for the MgO in x-ray diffraction pattern and d² is also confirmed which is evidence of little change in the film crystallinity during growth. These mean that the surface morphology of the TiO₂ films at d>10 nm keeping their crystallinity is determined from the statistical fluctuation in the impinging vapor flux. © 2000 American Vacuum Society.

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68.35.B-	Structure of clean surfaces (and surface reconstruction)
81.15.Cd	Deposition by sputtering
68.55.-a	Thin film structure and morphology

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A conductance model (approach) for kinetic studies: The Ti–Ta–Si system

Joshua Pelleg and L. Rubinovich

J. Vac. Sci. Technol. A 18, 2709 (2000); http://dx.doi.org/10.1116/1.1319678 (6 pages) | Cited 3 times

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Electrical resistance measurements provide a convenient way to study the kinetics of transformations in isothermally annealed thin films. The measured resistance and the amount of a new phase formed during some sort of reaction in a transformation process are often related by a linear function. This simple relationship between the measured resistance and the fraction of the new phase formed is not always valid and the reliability of the results might be questionable. In this communication, a different approach is suggested, which is based on conductance. The validity of the model is tested by experimental data for the Ti–Ta–Si system. The suggested and the linear resistance models are compared, and it seems that it is more appropriate in certain cases to use the conductance approach for kinetic purposes. An effective activation energy can be derived from the results by defining the time needed at each temperature to obtain either a constant resistance, or alternatively, a certain fraction of the new phase. The activation energy derived for the end phase, i. e. (Ti,Ta)Si₂ formation from the experimental data in the example (Ti–Ta–Si) considered is ∼2.6 eV. © 2000 American Vacuum Society.

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73.61.At	Metal and metallic alloys
61.72.Cc	Kinetics of defect formation and annealing
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Fx	Diffusion; interface formation
73.40.Ns	Metal-nonmetal contacts

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Microwave plasma nitriding of a low-alloy steel

D. Hovorka, J. Vlček, R. Čerstvý, J. Musil, P. Bělský, M. Růžička, and Jeon G. Han

J. Vac. Sci. Technol. A 18, 2715 (2000); http://dx.doi.org/10.1116/1.1308587 (7 pages) | Cited 7 times

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A low-alloy steel was nitrided in the downstream zone of an electron cyclotron resonance (ECR) discharge at low pressure (0.15–0.25 Pa). Structure and properties of the nitrided surfaces were primarily controlled by the substrate temperature T_s (300–550 °C), the nitrogen–hydrogen–argon gas mixture composition, and the substrate bias voltage U_b (−1000 to +40 V) at a typical value of the incident microwave power P_i=900 W, the distance of the substrate from output aperture of the ECR source was d=250 mm, and the nitriding time t=2 h. Optical emission spectroscopy was used to study the behavior of significant atomic and molecular species, such as N₂, N2+, NH, H, Fe, Ar, and Ar⁺, in front of the nitrided sample. It has been found that due to a high plasma reactivity, nitriding is effective at substrate temperatures T_s⩾500 °C, when the surface hardness is about 1200 HV_0.05 and a diffusion layer thickness up to 120 μm has been achieved for t=2 h. The presence of 10%–30% H₂ in a nitrogen–hydrogen gas mixture enhances the efficiency of nitriding in comparison with treatment in pure nitrogen under the same conditions. For T_s⩾500 °C, the process is effective even for substrates at positive potential (U_b=+30 V) and for a lower amount of N₂ (10%–30%) in a nitrogen–hydrogen–argon gas mixture, for which no compound layer is formed on the nitrided surface. However, the negative substrate bias voltage U_b enhances considerably the efficiency of nitriding only at lower substrate temperatures (T_s≈400 °C), when the nitriding is relatively weak. © 2000 American Vacuum Society.

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81.65.Lp

Surface hardening: nitridation, carburization, carbonitridation

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Measurement of beam-gas scattering lifetime in Pohang light source

C. D. Park, T.-Y. Lee, I. H. Bae, and S. M. Chung

J. Vac. Sci. Technol. A 18, 2722 (2000); http://dx.doi.org/10.1116/1.1319818 (6 pages) | Cited 1 time

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The beam-gas scattering lifetime of the Pohang light source (PLS) storage ring was studied. To eliminate the dominant Touschek effect for measurements of the beam-gas scattering lifetime, two methods were used separately: vacuum pressure increase by helium injection and very low electron beam density. Then two vertical beam scrapers were used to investigate the dependence of the Coulomb lifetime on the acceptance limiting aperture size. It was possible to obtain the separate ranges of Coulomb and bremsstrahlung lifetimes in the pressure range of normal operation. The results indicate that the vacuum is still an important factor for PLS, especially when small gap undulators are installed. © 2000 American Vacuum Society.

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29.20.db	Storage rings and colliders
29.27.Bd	Beam dynamics; collective effects and instabilities
41.75.Fr	Electron and positron beams
07.30.-t	Vacuum apparatus

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Estimation of the TEOS dissociation coefficient by electron impact

C. Vallée, A. Rhallabi, A. Granier, A. Goullet, and G. Turban

J. Vac. Sci. Technol. A 18, 2728 (2000); http://dx.doi.org/10.1116/1.1319820 (5 pages) | Cited 3 times

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SiO₂-like films are deposited in a low-pressure rf helicon reactor using oxygen-rich O₂/TEOS (tetraethoxysilane) mixtures. A model based on the deposition rate variation with the distance to the TEOS injection is used to estimate the TEOS electron-impact dissociation coefficient k_e and the effective sticking coefficient of reactive fragments s. In the helicon diffusion chamber where the electron temperature and density are about 4 eV and 10¹⁰ cm⁻³, respectively, k_e and s are found to be 1.82×10⁻⁷ cm³ s⁻¹ and 0.035, respectively. Under these low-pressure plasma conditions, the TEOS dissociation by electron impact is dominant over dissociation by oxygen atoms. © 2000 American Vacuum Society.

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34.80.Ht	Dissociation and dissociative attachment
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition

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Studies on plasma-nitrided iron by scanning electron microscopy, glancing angle x-ray diffraction, and x-ray photoelectron spectroscopy

Eduardo J. Miola, Sylvio D. de Souza, Pedro A. P. Nascente, Maristela Olzon-Dionysio, Carlos A. Olivieri, and Dirceu Spinelli

J. Vac. Sci. Technol. A 18, 2733 (2000); http://dx.doi.org/10.1116/1.1314392 (5 pages) | Cited 2 times

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The tribological and mechanical properties of several iron alloys are improved by nitriding processes. In this work the plasma process was employed because it offers various advantages as compared to other methods used in surface modifications. For example, it is a nonpollutant method and the nitriding times are reduced. Four samples were prepared by nitriding the iron substrates in a gas mixture of 80% of H₂ and 20% of N₂ under a pressure of 900 Pa, discharge frequency of 10 kHz and temperature of 500 °C, for 1, 2, 4, and 6 h. The samples were analyzed by optical microscopy, scanning electron microscopy (SEM), microhardness technique, glancing angle x-ray diffraction (GXRD), and x-ray photoelectron spectroscopy (XPS). SEM and GXRD results showed the presence of γ′-Fe₄N and a small amount of ϵ-Fe₃N phase. XPS was employed in order to obtain the chemical-state and quantitative informations on the plasma-nitrided iron surfaces. The surface N/Fe atomic ratios obtained by XPS were close to the ideal value of 0.25 for Fe₄N. The nitrogen concentration close to the surface is lower than that found in the bulk for all samples. This effect is explained by the presence of H₂ in the gas mixture, which not only cleans the surface but also removes nitrogen by sputtering. © 2000 American Vacuum Society.

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81.65.Lp	Surface hardening: nitridation, carburization, carbonitridation
81.05.Bx	Metals, semimetals, and alloys
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
68.35.Gy	Mechanical properties; surface strains
81.65.Cf	Surface cleaning, etching, patterning
62.20.Qp	Friction, tribology, and hardness
81.40.Np	Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Pq	Friction, lubrication, and wear
82.80.Pv	Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Dp	Adsorbed layers and thin films

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Scanning tunneling microscopy study of the Er/Ge(111) c(2×8) interface

S. Pelletier, E. Ehret, B. Gautier, F. Palmino, and J. C. Labrune

J. Vac. Sci. Technol. A 18, 2738 (2000); http://dx.doi.org/10.1116/1.1290377 (4 pages) | Cited 1 time

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Scanning tunneling microscopy (STM) is used to study the Er interaction on the Ge(111) substrate reconstructed c(2×8). In the submonolayer range, a homogeneous two-dimensional (2D) (1×1) reconstructed island distribution is observed for an Er deposit at room temperature with an additional annealing at 500 °C. However, when Er is deposited on substrate held at 500 °C, a significant modification in the surface morphology has been observed: 2D islands are accumulated at the step edges due to the high Ge and Er atom mobility. Moreover, for temperature under 500 °C, STM images have revealed the presence of metastable rod-shaped islands. Above 1 ML Er deposit, the interface displays a thin film reconstructed √3×√3R30° with a layer-by-layer growth mode. © 2000 American Vacuum Society.

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68.35.B-	Structure of clean surfaces (and surface reconstruction)
68.35.Rh	Phase transitions and critical phenomena
68.03.Fg	Evaporation and condensation of liquids
68.43.Mn	Adsorption kinetics
81.40.Gh	Other heat and thermomechanical treatments

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Etching of xerogel in high-density fluorocarbon plasmas

T. E. F. M. Standaert, E. A. Joseph, G. S. Oehrlein, A. Jain, W. N. Gill, P. C. Wayner, and J. L. Plawsky

J. Vac. Sci. Technol. A 18, 2742 (2000); http://dx.doi.org/10.1116/1.1290376 (7 pages) | Cited 32 times

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The etching of various xerogel films has been studied in high-density fluorocarbon plasmas. The xerogel etch rate is in part enhanced by the porosity. In discharges resulting in low surface polymerization, such as CF₄ or oxygen-rich fluorocarbon plasmas, an additional enhancement up to 60% is observed. When the polymerization of the discharge is increased, this additional enhancement disappears and the xerogel etch rate becomes more suppressed. The suppression is more pronounced for xerogel films with a higher porosity and a larger pore size. X-ray photoelectron spectroscopy analysis on partially etched samples shows that the suppression in etch rate is accompanied by an increasing amount of fluorocarbon material at the xerogel surface, especially in the pores of the xerogel structure. Finally, a 30% porous xerogel film was patterned using CHF₃ as an etching gas. Slight bowing of the sidewalls was observed. © 2000 American Vacuum Society.

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81.65.Cf	Surface cleaning, etching, patterning
61.43.Gt	Powders, porous materials
81.05.Rm	Porous materials; granular materials
82.70.Gg	Gels and sols
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
82.35.-x	Polymers: properties; reactions; polymerization
82.20.Pm	Rate constants, reaction cross sections, and activation energies
73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
82.80.Pv	Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.35.Dv	Composition, segregation; defects and impurities

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High density plasma oxide etching using nitrogen trifluoride and acetylene

Laura Pruette, Simon Karecki, Ritwik Chatterjee, Rafael Reif, Terry Sparks, and Victor Vartanian

J. Vac. Sci. Technol. A 18, 2749 (2000); http://dx.doi.org/10.1116/1.1290373 (10 pages) | Cited 4 times

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The use of nitrogen trifluoride (NF₃) and acetylene (C₂H₂) in the presence of helium has been examined for oxide etching in an inductively coupled, high density plasma etch tool. Oxide etch rates have been measured for blanket films and for patterned wafers with features of 0.6, 0.45, and 0.35 μm nominal critical dimension, while process performance has been assessed with cross-sectional scanning electron microscopy. Optical emission spectroscopy has been employed in situ to characterize the species present in the plasma, and quadrupole mass spectrometry has been used to analyze process effluent sampled between the chamber outlet and the turbo pump inlet. Polymer film deposited on the surface of the oxide layer has been studied with time-of-flight secondary ion mass spectrometry. Global warming emissions for a range of process conditions have been quantified using Fourier transform infrared spectroscopy, and are compared to emissions from more typical oxide etch processes on the same tool type. Results indicate that the NF₃/C₂H₂ chemistry is capable of etching oxide anisotropically, while offering a significantly lower global warming impact than current oxide etch chemistries. © 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

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Reaction layer dynamics in ion-assisted Si/XeF₂ etching: Temperature dependence

P. G. M. Sebel, L. J. F. Hermans, and H. C. W. Beijerinck

J. Vac. Sci. Technol. A 18, 2759 (2000); http://dx.doi.org/10.1116/1.1316102 (11 pages) | Cited 10 times

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We study the dynamics of the reaction layer during Ar⁺ ion-assisted Si etching by XeF₂ in the temperature range T=150–800 K. Depending on temperature, the etch rate can be enhanced a factor of 8 by ion bombardment. The dynamics are studied with ion-pulse measurements on a time scale of 1–100 s in a molecular beam setup. A reaction layer with a submonolayer fluorine coverage and dangling bonds is found to be formed on the Si(100) surface during ion bombardment. The dangling bond concentration increases with ion flux and is independent of temperature in the range 150–600 K. Chemisorption on these dangling bonds results in a higher reaction probability of XeF₂. The temperature dependence of the reaction probability of XeF₂ is fully determined by the temperature dependence of the XeF₂ precursor state. A simple model gives a very good description of the reaction probability as a function of both temperature and ion flux. The model description of the behavior of the precursor concentration as a function of ion flux and temperature is confirmed by ion pulse measurements on a time scale of 1 s. Further, it is concluded that the mechanisms for enhanced SiF₄ formation during ion bombardment are the same over the temperature range studied. © 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
73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.05.Cy	Elemental semiconductors

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Etching chemistry of benzocyclobutene (BCB) low-k dielectric films in F₂+O₂ and Cl₂+O₂ high density plasmas

Steven A. Vitale, Heeyeop Chae, and Herbert H. Sawin

J. Vac. Sci. Technol. A 18, 2770 (2000); http://dx.doi.org/10.1116/1.1310655 (9 pages) | Cited 21 times

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The etching chemistry of benzocyclobutene (BCB) low-k dielectric films was studied in a high density plasma etcher using F₂+O₂ and Cl₂+O₂ plasmas. The etching rate in F₂+O₂ plasmas exceeded 1.2 μm/min with selectivity over oxide and nitride of 16 and 32, respectively. The etching rate in Cl₂+O₂ plasmas exceeded 0.6 μm/min with selectivity over oxide and nitride of 40 and 80, respectively. BCB films do not etch in pure Cl₂ or pure O₂ plasmas without ion bombardment, but etching rates of 1000 Å/min were observed using F₂ plasmas without ion bombardment. The ion flux in F₂+O₂ plasmas is primarily O2+ and O⁺, whereas in Cl₂+O₂ the dominant ion is ClO⁺. BCB etching yields in F₂+O₂ plasmas were measured with a plasma beam/quartz crystal microbalance system. The etching yields suggest that the neutral fluxes and surface chemistry control the etching rates under these conditions, not the ion flux. Using x-ray photoelectron spectroscopy, it was determined that oxygen plasmas preferentially remove the carbon content of BCB, leaving behind a silicon oxide surface. Chlorine plasmas preferentially remove the silicon, leaving behind a carbon surface. F₂+O₂ plasmas etch BCB through a fluorocarbon film layer, the thickness of which increases with increasing fluorine concentration in the plasma. © 2000 American Vacuum Society.

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81.65.Cf	Surface cleaning, etching, patterning
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
77.55.-g	Dielectric thin films
82.80.Pv	Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

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Codeposition on diamond film surface during reactive ion etching in SF₆ and O₂ plasmas

K. Teii, M. Hori, and T. Goto

J. Vac. Sci. Technol. A 18, 2779 (2000); http://dx.doi.org/10.1116/1.1316098 (6 pages) | Cited 3 times

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The surface of polycrystalline diamond films during reactive ion etching in electron cyclotron resonance SF₆ and O₂ plasmas has been examined by scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. A SF₆ plasma required a high voltage in negative substrate biasing in order to achieve an equivalent etching rate to an O₂ plasma. This was ascribed to the codeposition effects and the low mean energy of ions upon impact in a SF₆ plasma. The elemental composition of the amorphous layer formed at the etched film surface in the two plasmas was almost equivalent and mainly composed of carbon and oxygen, except a low concentration (⩽1%) of sulfur and fluorine in the case of a SF₆ plasma. The significant codeposition on diamond surface was the most likely the result of plasma–wall interactions induced by the fragments from SF₆, and highly responsible for suppressing the ratio of lateral to vertical etching rate leading to anisotropic etching in a SF₆ plasma, in contrast with the little or no codeposition leading to isotropic etching in an O₂ plasma. The results give the substantial implications for the etching process in practical SF₆/O₂ plasmas utilized in device fabrication. © 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
81.65.Cf	Surface cleaning, etching, patterning
78.30.Am	Elemental semiconductors and insulators
79.60.Bm	Clean metal, semiconductor, and insulator surfaces

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Ion fluxes and energies in inductively coupled radio-frequency discharges containing C₂F₆ and c-C₄F₈

A. N. Goyette, Yicheng Wang, M. Misakian, and J. K. Olthoff

J. Vac. Sci. Technol. A 18, 2785 (2000); http://dx.doi.org/10.1116/1.1308590 (6 pages) | Cited 24 times

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We report ion energy distributions (IEDs), relative ion intensities, and absolute total ion current densities at the grounded electrode of an inductively coupled Gaseous Electronics Conference (GEC) radio-frequency (rf) reference cell for discharges generated in pure C₂F₆, c-C₄F₈, and in mixtures of each gas with Ar. These discharges contain several ions of significant intensity, with the dominant ion seldom that expected from direct ionization of the feed gas. Neither the C₂F₆ nor the c-C₄F₈ fraction in the Ar mixtures significantly influences the reactive ion composition. IEDs vary from single peaked to bimodal, the latter indicating rf modulation of the ions’ energy as they traverse the plasma sheath. Elevated gas pressures and higher fractions of either C₂F₆ or c-C₄F₈ all result in comparatively broader and more bimodal IEDs. IEDs in pure c-C₄F₈ discharges, compared to C₂F₆ discharges, generally exhibit more pronounced broadening and bimodality.

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52.80.Pi	High-frequency and RF discharges
52.25.-b	Plasma properties

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Angular dependence of SiO₂ etching in a fluorocarbon plasma

Byeong-Ok Cho, Sung-Wook Hwang, Gyeo-Re Lee, and Sang Heup Moon

J. Vac. Sci. Technol. A 18, 2791 (2000); http://dx.doi.org/10.1116/1.1318193 (8 pages) | Cited 27 times

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SiO₂ etch rates in a CF₄ plasma were obtained at various surface angles using a Faraday cage with pinholes on the upper plane through which ions are incident on the substrate fixed at various angles inside the cage. The reactive ion etching experiments were performed at 5 mTorr in a wide bias-voltage range from −100 to −800 V. The normalized etch-yield curves showed virtually the same angular dependence regardless of the ion incident energy. The curve shape was similar to that of physical sputtering except that the ratio of the maximum yield to that at 0° was as low as about 1.3. This is the deviation from the cosine dependence characteristic of chemical sputtering, which is the main mechanism of SiO₂ etching in a fluorocarbon plasma. This deviation is partly attributed to the fluorocarbon polymer film, which existed as a few monolayers-thick film on the substrate surface at low angles near 0° but as a submonolayer at high angles between 45° and 75°. The effect of the film-coverage difference on the deviation is explained in terms of reactant chemisorption, product desorption, energy deposited by ions causing the collision cascade, and incorporation of projectiles and recoils leading to the mixing effect. The deviation is also attributed to physical sputtering, which became comparable to chemical sputtering as the ion energy increased. Both factors, i.e., the formation of the thin fluorocarbon polymer film and physical sputtering, are supposed to contribute to the curve deviation, although their relative importance changed with the ion incident energy. © 2000 American Vacuum Society.

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81.65.Cf	Surface cleaning, etching, patterning
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
82.20.Pm	Rate constants, reaction cross sections, and activation energies
68.03.Fg	Evaporation and condensation of liquids
68.43.Mn	Adsorption kinetics
68.43.-h	Chemisorption/physisorption: adsorbates on surfaces

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Tantalum etching with a nonthermal atmospheric-pressure plasma

V. J. Tu, J. Y. Jeong, A. Schütze, S. E. Babayan, G. Ding, G. S. Selwyn, and R. F. Hicks

J. Vac. Sci. Technol. A 18, 2799 (2000); http://dx.doi.org/10.1116/1.1310652 (7 pages) | Cited 32 times

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Tantalum was etched in a downstream, atmospheric-pressure plasma. In this process, etching occurred without significant ion bombardment. An etching rate of 6.0±0.5 μm/min was achieved using 14.8 Torr oxygen, 22.4 Torr carbon tetrafluoride, 720±5 Torr helium, 685 W radio frequency power at 13.56 MHz, and a film temperature of 300 °C. The etching rate increased with the applied power, carbon tetrafluoride pressure, oxygen pressure, and residence time of the gas between the electrodes, indicating that the surface reaction depends on the density of reactive fluorine species generated in the plasma. X-ray photoemission spectroscopy revealed that the etched surface was covered with tantalum fluoride and to a lesser extent, tantalum oxide. Based on these observations, a mechanism for tantalum etching is proposed which involves the reaction between fluorine atoms and the adsorbed tantalum fluoride. © 2000 American Vacuum Society.

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81.65.Cf	Surface cleaning, etching, patterning
81.05.Bx	Metals, semimetals, and alloys
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
79.60.Dp	Adsorbed layers and thin films
73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.55.-a	Thin film structure and morphology

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Control of the radio-frequency wave form at the chuck of an industrial oxide-etch reactor

Lee Berry, Helen Maynard, Paul Miller, Tony Moore, Michael Pendley, Victoria Resta, Dennis Sparks, and Qingyun Yang

J. Vac. Sci. Technol. A 18, 2806 (2000); http://dx.doi.org/10.1116/1.1319819 (9 pages) | Cited 7 times

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Radio frequency (rf) power is commonly applied to the chuck of a high-density plasma reactor in order to extract ions and to control the energy of the ions used for the fabrication of microelectronic devices. In many cases, the temporal shape of the rf wave form largely determines the shape of the spectrum of those extracted ions, thereby strongly affecting feature evolution. Using auxiliary rf circuits, we successfully made major changes to the rf-potential wave form at the chuck of an Applied Materials 5300 HDP Omega reactor without affecting the normal functioning of the reactor’s control systems. This work established the practical feasibility of techniques for modifying the ion energy distribution functions of industrial reactors. © 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

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New very high frequency plasma source using a TM₀₁-mode patch antenna with short pins

Tomohiro Okumura, Takuya Matsui, Hideo Suzuki, and Kazuyuki Sakiyama

J. Vac. Sci. Technol. A 18, 2815 (2000); http://dx.doi.org/10.1116/1.1310654 (7 pages) | Cited 1 time

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We evaluated the basic characteristics of a new very high frequency (VHF) plasma source using a TM₀₁-mode patch antenna with short pins. The antenna comprises a round dielectric plate and a round metal plate which is grounded by short pins isotropically arranged. Electromagnetic field simulation has verified the isotropic distribution of both electric and magnetic fields. Ion-saturated current density measurements (Cl₂=100 sccm, 1 Pa and VHF power=1000 W) by placing the antenna in a cylindrical etching chamber 450 mm in diameter and 217 mm deep have revealed that uniform plasma is generated if a circular slit is positioned properly; that higher ion density is attained with dielectric plate relative permittivity set at 20, than at 7; and that increased VHF power causes proportional increase in ion density without giving rise to mode jumping or hysteresis. Experiment has revealed that the plasma source subject to our study provides superior ignitability, being capable of starting discharge even under 0.1 Pa. Experimental etching of polycrystalline silicon using this plasma source has yielded satisfactory results that etch rate is 183.5 nm/min±3.68%, poly-Si selectivity against resist is 4.8, and that against oxide film is 280 in main etching. © 2000 American Vacuum Society.

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52.50.Dg	Plasma sources
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
81.65.Cf	Surface cleaning, etching, patterning
81.05.Cy	Elemental semiconductors
52.40.Fd	Plasma interactions with antennas; plasma-filled waveguides
52.40.Db	Electromagnetic (nonlaser) radiation interactions with plasma
52.80.Pi	High-frequency and RF discharges
52.25.-b	Plasma properties

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Remote plasma enhanced metalorganic chemical vapor deposition of TiN from tetrakis-dimethyl-amido-titanium

Ju-Young Yun, Shi-Woo Rhee, Sanggee Park, and Jae-Gab Lee

J. Vac. Sci. Technol. A 18, 2822 (2000); http://dx.doi.org/10.1116/1.1316103 (5 pages) | Cited 8 times

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Effect of H₂ and N₂ plasma in the remote plasma enhanced metalorganic chemical vapor deposition of TiN (titanium nitride) from tetrakis-dimethyl-amido-titanium was studied in the deposition temperature range of 200–400 °C. The deposition rate with H₂ plasma is faster than with N₂ plasma and both processes showed similar activation energies, 16.7 and 18.3 kcal/mol, in the deposition temperature range of 200–300 °C. Above this temperature range, the deposition rate was decreased due to the gas phase dissociation of the precursor. H₂ plasma was effective in removing hydrocarbon impurities and carbon was incorporated as a form of TiC but with N₂ plasma, TiN film was formed with rough surface due to the incorporation of free carbon. The film with H₂ plasma showed low resistivity due to the lower incorporation of free carbon. © 2000 American Vacuum Society.

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81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
68.35.B-	Structure of clean surfaces (and surface reconstruction)
73.61.Ng	Insulators

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Effect of hydrogen dilution on the structure of SiOF films prepared by remote plasma enhanced chemical vapor deposition from SiF₄-based plasmas

J. C. Alonso, E. Pichardo, V. Pankov, and A. Ortiz

J. Vac. Sci. Technol. A 18, 2827 (2000); http://dx.doi.org/10.1116/1.1308593 (8 pages) | Cited 3 times

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Structural and electrical properties of fluorinated silicon dioxide (SiOF) films prepared by remote plasma enhanced chemical vapor deposition from the SiF₄–O₂–H₂–He gas mixture have been studied using ellipsometry, Fourier transform infrared spectroscopy, transmission electron microscopy, and current–voltage measurements. It has been found that the level of hydrogen dilution strongly affects the microstructure of deposited SiOF films. The films prepared at the H₂ flow rate below about 0.8 sccm have a biphase structure consisting of an amorphous matrix with the incorporation of 5–30 nm sized particles. The main origin of these particles seems to be gas phase oxidation of SiF_x species (with x=1, 2, 3) in plasma and downstream regions. Resulting films are characterized by extremely low density, reduced structural homogeneity, and poor electrical properties. Increase in the H₂ flow rate above 0.8 sccm completely suppresses the incorporation of particles into the growing film probably due to effective hindering gas phase oxidation process and results in dense homogeneous amorphous SiOF films with good electrical properties. © 2000 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
73.61.Ng	Insulators
78.66.Nk	Insulators
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
78.35.+c	Brillouin and Rayleigh scattering; other light scattering

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Properties and the influences on plasma performance for the film produced by radio frequency boronization

J. Li, Y. P. Zhao, X. Z. Gong, B. N. Wan, X. M. Gu, J. R. Luo, S. D. Zhang, C. F. Li, Y. C. Fang, M. Zhen, X. M. Wang, J. S. Hu, S. F. Li, J. K. Xie, and Y. X. Wan

J. Vac. Sci. Technol. A 18, 2835 (2000); http://dx.doi.org/10.1116/1.1308589 (8 pages) | Cited 3 times

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A new boronization technique focusing on the needs of the future large superconducting device has been developed in HT-7 tokamak. The first try on a tokamak gave very promising results. A fine homogeneous and hard a-B/C:H film was produced by a pulse ion cyclotron resonance frequency plasma. The film shows high adhesion, high thickness and longer lifetime. The ratio of B/C is about 3 up to a depth of 280 nm. X-ray photoelectron spectroscopy analysis shows that the B–B, B–C, C–C, C–O, and B–O bonds were formed during the boronization. The oxygen content in the film increases from 15% to 25% after 250 serious discharges, which demonstrated the strong oxygen gettering by the film. Good uniformity of the film in both toroidal and poloidal directions has been obtained by using long antenna on the high field side. The recycling of hydrogen was easily controlled by using helium rf discharge after boronization, and very strong wall pumping was observed. Plasma performance was significantly improved after boronization. A higher density limit and wider operation space were obtained. The strong hard x ray accompanied by high power lower hybrid current drive was suppressed dramatically. This gives direct evidence that the thin boron film serves as a protecting layer against the energetic particles, which is very important for future long-pulse-length discharge. This new technique has been proved to be very effective for conditioning future large magnetic fusion devices. © 2000 American Vacuum Society.

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52.80.Pi	High-frequency and RF discharges
52.55.Fa	Tokamaks, spherical tokamaks
68.60.Bs	Mechanical and acoustical properties
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
81.15.Kk	Vapor phase epitaxy; growth from vapor phase
82.80.Pv	Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

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Characterization of step coverage change in ultraviolet-transparent plasma enhanced chemical vapor deposition silicon nitride films

J. Bierner, M. Jacob, and H. Schönherr

J. Vac. Sci. Technol. A 18, 2843 (2000); http://dx.doi.org/10.1116/1.1314394 (4 pages) | Cited 7 times

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Ultraviolet (UV)-transparent silicon nitride films were deposited in a plasma enhanced chemical vapor deposition reactor. The dependence of the film properties on process parameters has been studied. UV transmittance, refractive index, hydrogen content, and step coverage were compared to UV-opaque films. A significant difference in film growth between UV-opaque and UV-transparent SiN_x layers has been detected. When film properties shift to an increased UV transparency, step coverage worsens significantly. This phenomenon is suggested to be caused by a strong reduction to Si–Si bonds for films below stoichiometric composition at low SiH₄/NH₃ gas flow ratios. © 2000 American Vacuum Society.

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81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
68.55.-a	Thin film structure and morphology
81.05.Je	Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk	Insulators
61.50.Lt	Crystal binding; cohesive energy

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Epitaxial growth of GaN using reactive neutrals extracted from the nitrogen Helicon wave plasma

Ki-Sung Kim and Seon-Hyo Kim

J. Vac. Sci. Technol. A 18, 2847 (2000); http://dx.doi.org/10.1116/1.1319676 (7 pages) | Cited 2 times

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A GaN epilayer on sapphire (0001) was grown using the N₂ Helicon wave plasma assisted evaporation deposition process. Various methods to reduce the N₂ ion impingement energy were attempted. The addition of inert gas (Ar, Ne) into the N₂ plasma decreased the impingement of N₂ ions and generated a higher quantity of activated nitrogen. In addition, the installation of mirror-type magnets effectively reduced the ion impingement energy. Although the ion impingement energy was less than the threshold (∼25 eV) for damaging GaN, the high flux of ion impingement during the growth of GaN induced a considerable strain in the epilayer. GaN film synthesized under direct ion impingement onto the growing surface has poor luminescent properties, despite its relatively good crystallinity. When the neutral nitrogen was utilized for GaN epilayer growth, the crystallinity and luminescent properties were greatly improved. Furthermore, with the decreasing of kinetic energy of fast neutral nitrogen, the in-plane crystallinity of GaN was improved and thus, an enhancement of luminescent properties was attained. © 2000 American Vacuum Society.

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81.05.Ea	III-V semiconductors
81.15.Kk	Vapor phase epitaxy; growth from vapor phase
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition
78.55.Cr	III-V semiconductors
78.66.Fd	III-V semiconductors

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Microstructure of Cu film sputter deposited on TiN

Akira Furuya, Yoshio Ohshita, and Atsuhi Ogura

J. Vac. Sci. Technol. A 18, 2854 (2000); http://dx.doi.org/10.1116/1.1310653 (4 pages) | Cited 2 times

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The correlation between the microstructure of Cu films and the deposition conditions of the sputtering method was investigated to obtain larger grain size and higher (111) texture. Cu film was deposited on SiO₂ and TiN by varying substrate temperature, Ar gas pressure, and rf power. It is found that the texture of the Cu film has very little dependence on the deposition conditions. The Cu grains are more oriented to (111) on a TiN substrate than on a SiO₂ substrate, and the (111) ratio of the Cu films on the TiN substrate increases as the (111) ratio of the TiN film is increased. The maximum increase in grain size was tenfold by reducing the Ar pressure from 3 to 1 mTorr, fivefold by increasing the deposition temperature from room temperature to 300 °C, and twofold by increasing the sputtering power from 1.1 to 4.4 W/cm². Thus, it is revealed that the lowering of Ar gas pressure is the dominant factor for enlarging the grain size. An increase in the energy of Cu particles brought about by reducing the Ar gas pressure is discussed as one of the factors contributing to the increase in the grain size. © 2000 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
61.72.-y	Defects and impurities in crystals; microstructure

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An anomalous erosion of a rectangular magnetron system

Eiji Shidoji, Masaharu Nemoto, and Takuji Nomura

J. Vac. Sci. Technol. A 18, 2858 (2000); http://dx.doi.org/10.1116/1.1312376 (6 pages) | Cited 13 times

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Monte Carlo simulations were performed to examine the dc magnetron discharge that creates anomalous erosion at the boundary of the curved and straight sections of a rectangular magnetron. In order to examine the cause of anomalous erosion, we performed a series of simulations describing the strong and weak field regions without the curved section. The erosion profiles were calculated under differing magnetic field distributions. We found that anomalous erosion occurs under a magnetic field of more than 200 G. We also found that the cause of anomalous erosion is the weak magnetic field at the curved section as compared to that at the straight section. We confirmed that anomalous erosion does not occur in the case of a rectangular magnetron having a uniform magnetic field. In order to avoid anomalous erosion, the uniformity of the magnetic field has to be within 10% where the vertical component of the magnetic field at the target surface is zero. © 2000 American Vacuum Society.

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79.20.Rf	Atomic, molecular, and ion beam impact and interactions with surfaces
62.20.Qp	Friction, tribology, and hardness
81.40.Pq	Friction, lubrication, and wear

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Photoluminescence and heteroepitaxy of ZnO on sapphire substrate (0001) grown by rf magnetron sputtering

Kyoung-Kook Kim, Jae-Hoon Song, Hyung-Jin Jung, Won-Kook Choi, Seong-Ju Park, Jong-Han Song, and Jeong-Yong Lee

J. Vac. Sci. Technol. A 18, 2864 (2000); http://dx.doi.org/10.1116/1.1318192 (5 pages) | Cited 31 times

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ZnO thin films were epitaxially grown on α-Al₂O₃ (0001) single-crystal substrates by rf magnetron sputtering. The films were grown at substrate temperatures of 550–600 °C for 1 h at a rf power of 60–120 W and Ar/O₂ ratios of 1–4. The crystalline structure of the ZnO films was analyzed by four-circle x-ray diffraction (XRD) and Rutherford backscattering (RBS)/channeling. For the ZnO films deposited at 550 °C, the full width at half maximum (FWHM) of the XRD θ-rocking curve of the ZnO (0002) plane was found to be increased from 0.16° to 0.3° as the rf power was increased from 80 to 120 W. The in-plane epitaxial relationship of the ZnO film on α-Al₂O₃ (0001) substrates was found to be ZnO [10 math

0]∥α-Al₂O₃[11 math

0], indicating a 30° rotation of the ZnO unit cell with respect to the α-Al₂O₃ (0001) substrate. For the specimen grown at 600 °C, the FWHM of the XRD θ-rocking curve was 0.13°. In RBS/channeling studies, the films, which were deposited at 600 °C and 120 W, showed good crystallinity, with a channeling yield minimum (χ_min) of only 3.5%, whereas χ_min for the films deposited at 550 °C was as high as 50%–60%, indicating poor crystalline quality. In the case of photoluminescence (PL) measurements, sharp near-band-edge emission was observed at room temperature. The FWHM of the PL peak decreased from 133 to 89 meV at a growth temperature 550 °C by increasing the rf power. For the films deposited at 600 °C, a FWHM of the PL peak of 75–90 meV was observed, which is the lowest value reported to date. From the results of both XRD and PL measurement, it was found that the crystallinity of the films grown at 550 °C improved, but its optical property degraded. With increasing rf power, the films show a deep-level emission in the presence of higher mixtures of Ar:O₂ because a considerable amount of activated oxygen was supplied in the ZnO films with an increase of rf power. From transmission electron microscopy and atomic force microscope analyses, the grain size and defects were found to affect the PL properties. The relationship between optical properties and crystal quality is discussed in terms of crystalline structure and grain size. © 2000 American Vacuum Society.

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78.66.Hf	II-VI semiconductors
78.55.Et	II-VI semiconductors
81.05.Dz	II-VI semiconductors
68.55.-a	Thin film structure and morphology
81.15.Cd	Deposition by sputtering
61.85.+p	Channeling phenomena (blocking, energy loss, etc.)
82.80.Yc	Rutherford backscattering (RBS), and other methods of chemical analysis

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Optical and microstructural properties of MgF₂ UV coatings grown by ion beam sputtering process

E. Quesnel, L. Dumas, D. Jacob, and F. Peiró

J. Vac. Sci. Technol. A 18, 2869 (2000); http://dx.doi.org/10.1116/1.1290374 (8 pages) | Cited 9 times

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The optical, mechanical, and microstructural properties of MgF₂ single layers grown by ion beam sputtering have been investigated by spectrophotometric measurements, film stress characterization, x-ray photoelectron spectroscopy (XPS), x-ray diffraction, and transmission electron microscopy. The deposition conditions, using fluorine reactive gas or not, have been found to greatly influence the optical absorption and the stress of the films as well as their microstructure. The layers grown with fluorine compensation exhibit a regular columnar microstructure and an UV-optical absorption which can be very low, either as deposited or after thermal annealings at very low temperatures. On the contrary, layers grown without fluorine compensation exhibit a less regular microstructure and a high ultraviolet absorption which is particularly hard to cure. On the basis of calculations, it is shown that F centers are responsible for this absorption, whereas all the films were found to be stoichiometric, in the limit of the XPS sensitivity. On the basis of external data taken from literature, our experimental curves are analyzed, so we propose possible diffusion mechanisms which could explain the behaviors of the coatings. © 2000 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
42.79.Wc	Optical coatings
78.40.Ha	Other nonmetallic inorganics
79.60.Dp	Adsorbed layers and thin films
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.60.Bs	Mechanical and acoustical properties

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Influence of Pt underlayer on the magnetic and magneto-optical properties of sputtered Co_0.25Pt_0.75 alloy films, and the static recording performance

Z. Q. Zou, K. W. Kim, Y. P. Lee, M. Li, and D. F. Shen

J. Vac. Sci. Technol. A 18, 2877 (2000); http://dx.doi.org/10.1116/1.1308588 (7 pages)

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Influences of a Pt underlayer and the preparing conditions on the magnetic and magneto-optical (MO) properties of Co_0.25Pt_0.75 alloy films, which were prepared by sputtering using a composite target, were investigated. It was found that a good fcc (111) texture was formed in a Pt underlayer deposited in a sputtering pressure below 2 Pa even without heating the substrate. Co_0.25Pt_0.75 alloy films subsequently deposited on such a Pt underlayer exhibited an enhanced perpendicular magnetic anisotropy, and the growth temperature for excellent magnetic and MO properties was lowered to 150 °C. Static read–write experiments on the Co_0.25Pt_0.75 alloy films showed that the static signals could be easily written, at a moderate recording power, in the alloy films without a Pt underlayer, and that the introduction of a relatively thick Pt underlayer was not beneficial to the thermomagnetic writing for the alloy films. The large readout signals of an Al/ZnS/Co_0.25Pt_0.75/glass trilayer structure suggest that Co_xPt_1−x alloy films are a promising candidate for the advanced MO recording media. © 2000 American Vacuum Society.

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75.70.Ak	Magnetic properties of monolayers and thin films
78.20.Ls	Magneto-optical effects
75.50.Ss	Magnetic recording materials
75.30.Gw	Magnetic anisotropy
81.15.Cd	Deposition by sputtering
68.55.-a	Thin film structure and morphology
78.66.Bz	Metals and metallic alloys

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Residual stress formation in multilayered TiN/TaN_x coatings during reactive magnetron sputter deposition

M. Nordin, M. Larsson, T. Joelsson, J. Birch, and L. Hultman

J. Vac. Sci. Technol. A 18, 2884 (2000); http://dx.doi.org/10.1116/1.1308594 (6 pages) | Cited 1 time

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Multilayered physical vapor deposited TiN/TaN_x coatings were deposited on cemented carbide substrates using a dual target magnetron sputtering system. The coatings were investigated with respect to the influence of nitrogen partial pressure during deposition on the residual stress developed in the coatings. Furthermore, the fracture strength of the material, i.e., the magnitude of the tensile stress that the coating can support without cracking, was evaluated. It was found that, by increasing the nitrogen partial pressure, it is possible to change the stress from compressive to tensile. The highest tensile stress was about 3.6 GPa. Despite this high stress, the coating displayed no cracking. This implies that it is possible to grow TiN/TaN_x multilayered coatings with high tensile fracture strength using dual magnetron sputtering and a high deposition temperature (about 680 °C). © 2000 American Vacuum Society.

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68.60.Bs	Mechanical and acoustical properties
68.65.-k	Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Cd	Deposition by sputtering
62.20.M-	Structural failure of materials
81.40.Np	Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

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Reactive pulsed magnetron sputtering process for alumina films

P. J. Kelly, P. S. Henderson, R. D. Arnell, G. A. Roche, and D. Carter

J. Vac. Sci. Technol. A 18, 2890 (2000); http://dx.doi.org/10.1116/1.1319679 (7 pages) | Cited 32 times

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The pulsed magnetron sputtering (PMS) process is now among the leading techniques for the deposition of oxide films. In particular, the use of pulsed dc power has transformed the deposition of dielectric materials, such as alumina. The periodic target voltage reversals during the PMS process effectively discharge poisoned regions on the target. This significantly reduces the occurrence of arc events at the target and stabilizes the deposition process. Many researchers have now shown that pulsed dc reactive magnetron sputtering can be routinely used to produce fully dense, defect-free oxide films. Despite the success of the PMS process, few detailed studies have been carried out on the role played by parameters such as pulse frequency, duty cycle, and reverse voltage in the deposition process. In this study, therefore, alumina films were deposited by reactive pulsed dc magnetron sputtering. Operating conditions were systematically varied and the deposition process monitored throughout. The aim was to investigate the influence of the pulse parameters on the deposition process, and the interrelationships between the occurrence of arc events and the parameters chosen. As a result of this investigation, optimum conditions for the production of high-quality alumina films under hard arc-free conditions were also identified. © 2000 American Vacuum Society.

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81.15.Cd	Deposition by sputtering
85.40.Sz	Deposition technology
77.55.-g	Dielectric thin films

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Ionization of sputtered material in a planar magnetron discharge

C. Christou and Z. H. Barber

J. Vac. Sci. Technol. A 18, 2897 (2000); http://dx.doi.org/10.1116/1.1312370 (11 pages) | Cited 29 times

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Emission spectra in the visible and near ultraviolet have been recorded for the magnetron sputtering of titanium by argon at pressures between 0.5 and 100 Pa. Intense emission lines from both atomic and ionic material were detected, and comparison of line intensities yielded an ionization fraction of over 10% and an electron temperature of the order of 1 eV for the sputtered material. The ionization fraction decreased with increasing magnetron power, and an optimal operating pressure was found for maximum ion content of the sputtered flux. Scaling laws of emission line intensity with magnetron power indicated the incomplete thermalization of sputtered metal with the sputtering plasma, and spatially resolved measurements of ionization profiles were used to investigate the transport and collisional ionization of sputtered material. Penning ionization of sputtered titanium by metastable argon was found to be the dominant ionization process, and the effect of diffusion of metastable argon was noted. Control of ion content in sputtered fluxes is of interest for the deposition of thin films and for metallization of semiconductors. © 2000 American Vacuum Society.

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52.80.Sm	Magnetoactive discharges (e.g., Penning discharges)
79.20.Rf	Atomic, molecular, and ion beam impact and interactions with surfaces
52.70.Kz	Optical (ultraviolet, visible, infrared) measurements
81.15.Cd	Deposition by sputtering
85.40.Sz	Deposition technology
52.25.Fi	Transport properties
85.40.Ls	Metallization, contacts, interconnects; device isolation
52.25.-b	Plasma properties

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Reactive deposition of compounds by a cavity-hollow cathode direct current sputtering system

Mehdi H. Kazemeini and Alexander A. Berezin

J. Vac. Sci. Technol. A 18, 2908 (2000); http://dx.doi.org/10.1116/1.1312373 (6 pages) | Cited 2 times

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A new hollow cathode has been designed and applied in a reactive direct current (dc) sputtering system. This hollow cathode with an extra cavity (1.4 cm³) separates the reaction at the substrate from the reaction at the target surface and therefore prevents the target surface (cavity walls) to transit from the metallic sputter mode to the reactive sputter mode. This transition normally happens in reactive dc sputtering systems and it is the cause of a drastic drop in the deposition rate. The physical geometry of this cavity provides larger cathode walls and more efficient use of fast electrons and ions to produce large densities of sputtered and evaporated particles of the target metal. The development of this cavity-hollow cathode was facilitated by comprehensive structural and compositional analysis of some deposited films. By using pure titanium for the target and a mixture of 90%Ar/8%N₂/2%O₂ for the operating gas, some samples of titanium oxinitride films a few microns thick have been produced. At operating pressure of 0.05 Torr, the measured value for the cathode fall distance inside the cavity is 1.6 mm, showing that the pressure inside the cavity is much higher than the operating pressure in the reactor chamber. The current–voltage characteristics of this system exhibit a switching behavior from a nondischarge mode to a discharge mode with a negative resistance. © 2000 American Vacuum Society.

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81.15.Cd

Deposition by sputtering

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Microstructure and chemical state of Ti_1−xY_xN film deposited by reactive magnetron sputtering

W. S. Choi, S. K. Hwang, and C. M. Lee

J. Vac. Sci. Technol. A 18, 2914 (2000); http://dx.doi.org/10.1116/1.1319680 (8 pages) | Cited 6 times

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A feasibility of using Ti_1−xY_xN as a hard coating material was investigated. Coatings were made on a Si(100) surface as well as on a steel surface using a dual-target rf-dc reactive magnetron sputtering method with the range of Y varying from x=0 to x=0.16. By x-ray diffraction analysis, it was found that all the coated films were of a single phase with a NaCl structure, with their lattice parameters increasing with Y content. A transmission electron microscopy analysis of the coated film revealed fine columnar grains in the samples containing high NY. This was attributed to Y atoms of low surface mobility and a strong bonding tendency with oxygen. The Y atoms promote the rate of heterogeneous nucleation by easily forming fine oxide particles at the substrate surface. From x-ray photoelectron spectroscopy analysis, it was learned that the binding energies of Y 3d_5/2 and N 1s in YN bonding were 157.8 and 397.5 eV, respectively. The optimum combination of microhardness and adhesion strength was obtained in Ti_0.928Y_0.072N film. In an oxidation resistance test at 800 °C, the TiN films with high Y content performed better than pure TiN film. The oxide scale in this case consisted of rutile TiO₂, anatase TiO₂, and Y₂Ti₂O₇, in which Y 3d_5/2 and O 1s had binding energies of 158.7 and 530.8 eV, respectively. Overall, the present study suggests a good feasibility of utilizing Y in TiN hard coating material. © 2000 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
81.15.Cd	Deposition by sputtering
68.35.Gy	Mechanical properties; surface strains
68.60.Bs	Mechanical and acoustical properties
61.66.Fn	Inorganic compounds
62.20.Qp	Friction, tribology, and hardness
81.40.Pq	Friction, lubrication, and wear
81.65.Mq	Oxidation
79.60.Dp	Adsorbed layers and thin films
81.40.Np	Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

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Phase development in annealed zirconia-titania nanolaminates

J. D. DeLoach, J. J. Shibilski, C. R. Crape, and C. R. Aita

J. Vac. Sci. Technol. A 18, 2922 (2000); http://dx.doi.org/10.1116/1.1319681 (6 pages) | Cited 10 times

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Phase development was studied in sputter-deposited and annealed ZrO₂–TiO₂ nanolaminate films on fused silica substrates. The goal was to understand phase evolution as these structures moved toward thermodynamic equilibrium. The results show that diffusive amorphization to form α-ZTO was the first reaction of the as-deposited constituents at low temperature (700 °C). Growth of α-ZTO was self-limited, and a second metastable reaction product with an incommensurate α-PbO₂-type lattice, ss-ZTO, formed with time at temperature. Terminal phases formed only when the annealing temperature was raised to 1000 °C, thereby lifting kinetic constraints to diffusion. The terminal phases were ZrTiO₄ or ZrTi₂O₆, depending upon film stoichiometry. This study demonstrates that in the absence of a physical driving force to promote layer registration upon low temperature annealing, constituents react to lower the system’s free energy via a series of metastable phases that involve limited atomic rearrangement. Equilibrium phases are formed only after the kinetic constraints to diffusion are relaxed. © 2000 American Vacuum Society.

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61.46.-w	Structure of nanoscale materials
68.55.-a	Thin film structure and morphology
61.43.Er	Other amorphous solids
66.30.H-	Self-diffusion and ionic conduction in nonmetals
61.72.Cc	Kinetics of defect formation and annealing
61.66.Bi	Elemental solids
61.66.Dk	Alloys
65.20.-w	Thermal properties of liquids
65.40.gd	Entropy
81.30.Dz	Phase diagrams of other materials
64.70.K-	Solid-solid transitions

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Study of the double layer CeO₂/Nb₂O₅ thin film

Zaoli Zhang, Xinhua Du, and Wendong Wang

J. Vac. Sci. Technol. A 18, 2928 (2000); http://dx.doi.org/10.1116/1.1314393 (4 pages) | Cited 5 times

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A double layer CeO₂/Nb₂O₅ thin film by magnetron sputtering was prepared. The property and microstructure of the thin film were carefully characterized by x-ray photoelectron spectroscopy (XPS), transmission electron microscopy, and high resolution transmission electron microscopy. XPS measurement clearly demonstrated that the Nb₂O₅ layer underlying CeO₂ as a electrical-conductive layer could greatly improve the reduction ability of CeO₂ thin film compared with that of a single layer CeO₂ thin film. Fitting to the XPS experimental data and deconvoluting the spectra showed the increase of Ce³⁺ concentration in the double layer CeO₂/Nb₂O₅ thin film. The microstructure of the double layer thin film was composed of three distinguishable layers, which are a polycrystalline CeO₂ layer, an amorphous Nb₂O₅ layer, and an intermediate amorphous layer with regard to the silicon substrate. The interface between CeO₂ and Nb₂O₅ was rough and indistinct. A detailed analysis was given from the viewpoint of interdiffusion at the CeO₂/Nb₂O₅ interface. © 2000 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
81.05.Je	Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.35.Ct	Interface structure and roughness
81.15.Cd	Deposition by sputtering
79.60.Dp	Adsorbed layers and thin films
66.30.Ny	Chemical interdiffusion; diffusion barriers
68.35.Fx	Diffusion; interface formation

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Titanium oxide films on Si(100) deposited by e-beam evaporation

H. K. Jang, S. W. Whangbo, Y. K. Choi, Y. D. Chung, K. Jeong, C. N. Whang, Y. S. Lee, H-S. Lee, J. Y. Choi, G. H. Kim, and T. K. Kim

J. Vac. Sci. Technol. A 18, 2932 (2000); http://dx.doi.org/10.1116/1.1312377 (5 pages) | Cited 4 times

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Titanium oxide films with a thickness of a 400 nm were deposited on p-type Si(100) at room temperature by e-beam evaporation, and titanium dioxide was evaporated in oxygen environment at a pressure of 2×10⁻⁶–4×10⁻⁵ Torr. Effects of oxygen flow rate (F_O₂) on the properties of the films, such as surface roughness, composition, and chemical states, have been investigated. The root-mean-square surface roughness of the films increased with increasing F_O₂ up to 20 sccm, and then decreased over 20 sccm. X-ray diffraction patterns show that the titanium oxide films are amorphous. Oxygen resonance backscattering spectroscopy shows that all films are oxygen rich, i.e., relative atomic ratio (C_O/C_Ti) of the films ranged from 2.05 to 2.25. But the x-ray photoelectron spectroscopy (XPS) analysis shows that the titanium oxide films were oxygen deficient. The ratio of oxygen to titanium (C_O₂/C_Ti) of the films calculated by XPS ranged from 1.82 to 1.93. XPS shows that there exist only Ti³⁺ and Ti⁴⁺ charge states in the film. Ti⁴⁺ states of the films are nearly constant at 0.47 up to O₂ flow rate of 20 sccm, and then slightly increase with increasing O₂ flow rate. Although rutile TiO₂ is used as a starting material, titanium K-edge x-ray absorption near-edge spectroscopy (XANES) spectra show that the structure of the TiO_2−x films grown in oxygen environment are amorphous. The Ti K-edge XANES spectra from the films is the same regardless of F_O₂. © 2000 American Vacuum Society.

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81.15.-z	Methods of deposition of films and coatings; film growth and epitaxy
73.61.Ng	Insulators
79.60.Dp	Adsorbed layers and thin films
68.35.B-	Structure of clean surfaces (and surface reconstruction)
78.66.Nk	Insulators

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Monte Carlo modeling of electron beam physical vapor deposition of yttrium

Jing Fan, Iain D. Boyd, and Chris Shelton

J. Vac. Sci. Technol. A 18, 2937 (2000); http://dx.doi.org/10.1116/1.1310656 (9 pages) | Cited 7 times

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As part of a study on the deposition of superconducting films of YBa₂Cu₃O_7−δ, a three-dimensional electron beam physical vapor deposition process of yttrium in a vacuum chamber is investigated both computationally and experimentally. The numerical analysis employs the direct simulation Monte Carlo (DSMC) method. The experimental studies consist of atomic absorption spectra taken in the evaporated yttrium plume and deposited film thickness profiles. Some important modeling issues such as atomic collision cross sections for metal vapors and hyperfine electronic structure of the atomic absorption spectra are addressed. Film deposition thicknesses on the substrate and atomic absorption spectra given by the DSMC method and experiment are in excellent agreement. Collisions between the atoms are found to have a significant effect on the film growth rate and area of uniform deposition as the evaporation rate of yttrium increases. © 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
78.40.Kc	Metals, semimetals, and alloys
78.66.Bz	Metals and metallic alloys
71.70.Jp	Nuclear states and interactions

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Depth distribution of Bi⁺ and Fe⁺ implanted into polyimide (C₂₂H₁₀N₂O₅)_n

Ke-Ming Wang, Hui Hu, Fei Lu, Feng Chen, Jiang-Hua Zhang, Xiang-Dong Liu, Ji-Tian Liu, Bo Wu, and Mu-Bin Huang

J. Vac. Sci. Technol. A 18, 2946 (2000); http://dx.doi.org/10.1116/1.1316100 (4 pages)

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Polyimide (C₂₂H₁₀N₂O₅)_n was implanted with Bi⁺ and Fe⁺ ions at different energies, doses, and angles. The depth distribution of implanted Bi⁺ and Fe⁺ ions in polyimide was measured by Rutherford backscattering. The results show: (1) For the case of 2×10¹⁵ Bi⁺ ions/cm², the depth distribution was nearly Gaussian for both energies; for the case of 1×10¹⁶ Bi⁺ ions/cm², diffusion behavior during implantation is observed. (2) For the case of 1×10¹⁶ Fe⁺ions/cm², the depth distribution was Gaussian for 200 keV, and the depth distributions of the as-implanted Fe⁺ ions become bimodal and have a split behavior under 0° and 45° for 350 keV. (3) For a regular distribution, the experimental mean-projected range is in good agreement with the calculated value, within less than 6%, the experimental range straggling is larger than the calculated one based on TRIM'98. © 2000 American Vacuum Society.

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61.41.+e	Polymers, elastomers, and plastics
82.80.Yc	Rutherford backscattering (RBS), and other methods of chemical analysis

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Near-surface chemistry in Zr₂Fe and ZrVFe studied by means of x-ray photoemission spectroscopy: A temperature-dependent study

Janez Kovac, Oumar Sakho, Paolo Manini, and M. Sancrotti

J. Vac. Sci. Technol. A 18, 2950 (2000); http://dx.doi.org/10.1116/1.1308591 (7 pages) | Cited 4 times

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The near-surface atomic composition and the character of chemical bond in two nonevaporable gettering alloys have been investigated via core level (Zr 3d, Fe 2p, V 2p, O 1s, C 1s) photoemission. The samples have been measured in UHV after in-air fracturing and various annealing steps (up to 850 °C). For T>400 °C a progressive and sizeable decrease of the near surface C content along with an increase in the Zr concentration is observed in both alloys. An annealing induced Zr enrichment at the surface is found, the metallic atomic concentrations being significantly far from the nominal bulk stoichiometry. The annealing induces a strong evolution in the chemical bonds, the metallic species being completely oxidized in in-air fractured samples while a metallic character progressively emerges at increasing temperatures. Surface metallization proceeds faster in Zr₂Fe than in the V-containing getter. © 2000 American Vacuum Society.

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68.35.Dv	Composition, segregation; defects and impurities
79.60.Bm	Clean metal, semiconductor, and insulator surfaces
81.65.Tx	Gettering
82.80.Pv	Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.30.Cy	Vacuum pumps
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

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Dependence of optical properties on structural and compositional parameters in CuGaSe₂

R. Díaz, T. Martín, J. M. Merino, M. León, and F. Rueda

J. Vac. Sci. Technol. A 18, 2957 (2000); http://dx.doi.org/10.1116/1.1314391 (7 pages) | Cited 6 times

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The dielectric constant of CuGaSe₂ as a function of stoichiometric deviations has been obtained from photomodulated spectral ellipsometry measurements. Optical gaps have been computed by fitting experimental and differentiated data of the imaginary part of the dielectric constant to function ϵ₂ of the Lorentz model and to the second derivative of ϵ₂. In each sample, three transition energy values have been found in the 1.65–1.72, 1.83–1.95, and 2.97–3.14 eV ranges. The presence of point defects reduces the energy gap values. For nonstoichiometric samples, changes in the first energy gap values have been analyzed as a function of the displacement of the position of the anion in the unit cell. The shifts in the valence band structure have been analyzed and it is concluded that the difference between the first and second transition energies, (E_g2−E_g1), is also affected by stoichiometric deviations, so that the Γ5v(2) level in samples with point defects is closer to Γ4v(2) level than in stoichiometric ones. Changes in (E_g3−E_g2) and (E_g3−E_g1) are related to Se position. © 2000 American Vacuum Society.

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72.80.Jc	Other crystalline inorganic semiconductors
71.45.Gm	Exchange, correlation, dielectric and magnetic response functions, plasmons
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Nr	Semiconductor compounds
77.22.Ch	Permittivity (dielectric function)
61.72.J-	Point defects and defect clusters

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Role of delocalized nitrogen in determining the local atomic arrangement and mechanical properties of amorphous carbon nitride thin films

B. C. Holloway, O. Kraft, D. K. Shuh, W. D. Nix, M. Kelly, P. Pianetta, and S. Hagström

J. Vac. Sci. Technol. A 18, 2964 (2000); http://dx.doi.org/10.1116/1.1308592 (8 pages) | Cited 8 times

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We report the results of a comprehensive study of the mechanical properties and chemical structure of carbon nitride thin films deposited by magnetron sputtering. Nanoindentation measurements show that the films are very elastic. Using a modified Oliver–Pharr method, to account for the elasticity of the films, the reduced elastic modulus was calculated to fall in the range of 35–55 GPa for all films measured. No quantifiable plastic deformation was measured in the tested films, therefore the hardness calculated (6 GPa) can only be assumed to be a lower bound. Fourier transform infrared spectroscopy of the carbon nitride films indicates the presence of large amounts of single and double bonds, and very small amounts of triple bonding, between carbon and nitrogen. Near edge x-ray absorption fine structure data suggests that there are three predominant types of bonds between carbon and nitrogen. This is consistent with the x-ray photoelectron spectroscopy data which shows N(1s) and C(1s) core spectra with multiple, chemically shifted features. The data suggest, but do not confirm, the presence of nitrogen atoms participating in four bonds (three sigma, one pi). A self-consistent argument is presented that links parametric changes in mechanical properties with changes in a proposed film structure based on nitrogen participating in four bonds. This marks a new approach to the interpretation of nitrogen bonding with carbon in the solid state not only for amorphous carbon nitride, but also other systems such as diamond and boron nitride thin films. © 2000 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
68.60.Bs	Mechanical and acoustical properties
68.35.Gy	Mechanical properties; surface strains
61.43.-j	Disordered solids
81.15.Cd	Deposition by sputtering
62.20.D-	Elasticity
62.20.Qp	Friction, tribology, and hardness
78.66.Nk	Insulators
78.35.+c	Brillouin and Rayleigh scattering; other light scattering
79.60.Dp	Adsorbed layers and thin films

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Effect of Mg content in Cu(Mg)/SiO₂/Si multilayers on the resistivity after annealing in an oxygen ambient

Wonhee Lee, Heunglyul Cho, Bumseok Cho, Jiyoung Kim, Yong-suk Kim, Woo-Gwang Jung, Hoon Kwon, Jinhyung Lee, Chongmu Lee, P. J. Reucroft, and Jaegab Lee

J. Vac. Sci. Technol. A 18, 2972 (2000); http://dx.doi.org/10.1116/1.1316101 (6 pages) | Cited 12 times

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The formation mechanism of self-aligned MgO layers obtained from Cu(Mg) alloys has been investigated. Self-aligned surface and interfacial MgO layers were formed upon annealing Cu(Mg)/SiO₂/Si multilayer films in an oxygen ambient, resulting in a structure of MgO/Cu/MgO/SiO₂/Si. Upon annealing at 300 °C or higher in an oxygen ambient, Mg segregates preferentially to the Cu surface until a dense, uniform MgO layer is formed. A growth limited thickness of the surface MgO was found to be about 150 Å , providing substantial passivation of the exposed Cu surface. After a dense MgO layer forms, substantial Mg segregation to the SiO₂ surface takes place. However, the formation of the interfacial MgO caused a sudden increase in resistivity after annealing for about 20 min, which can be due to the release of free Si being diffused into the Cu film by the reaction of Mg with Si in the SiO₂. The optimum Mg contents in Cu(Mg) alloy films with various thickness were thus estimated to obtain the Cu(Mg) alloy multilayer film with substantially lower resistivity while retaining the beneficial properties of Cu passivation in an oxygen ambient. © 2000 American Vacuum Society.

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73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc	Kinetics of defect formation and annealing
64.75.-g	Phase equilibria
68.35.Fx	Diffusion; interface formation
81.65.Rv	Passivation

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Direct measurement of density-of-states effective mass and scattering parameter in transparent conducting oxides using second-order transport phenomena

D. L. Young, T. J. Coutts, V. I. Kaydanov, A. S. Gilmore, and W. P. Mulligan

J. Vac. Sci. Technol. A 18, 2978 (2000); http://dx.doi.org/10.1116/1.1290372 (8 pages) | Cited 45 times

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The Boltzmann transport equation can be solved to give analytical solutions to the resistivity, Hall, Seebeck, and Nernst coefficients. These solutions may be solved simultaneously to give the density-of-states effective mass (md∗), the Fermi energy relative to either the conduction or valence band, and a scattering parameter that is related to a relaxation time and the Fermi energy. The Nernst coefficient is essential for determining the scattering parameter and, thereby, the effective scattering mechanism(s). We constructed equipment to measure these four transport coefficients simultaneously over a temperature range of 30–350 K for thin, semiconducting films deposited on insulating substrates. We measured these coefficients for rf magnetron-sputtered zinc oxide, both doped and undoped, with aluminum with carrier concentrations in the range of 1×10¹⁹–5×10²⁰ cm⁻³. The (md∗) was not constant over this carrier concentration range: varying from 0.3 to 0.48 m_e, leading us to conclude that zinc oxide has a nonparabolic conduction band. Conductivity effective mass values for zinc oxide matched our md∗ values, revealing a single valley, nearly spherical, constant energy surface for zinc oxide. The measured scattering parameter changed from close to zero to 1.5 as the carrier concentrations increased. The scattering parameter, Seebeck coefficient, and mobility versus temperature data support neutral impurity scattering in the undoped material and ionized impurity scattering in the Al-doped ZnO. The transport theory also allows an extrapolation for an md∗ value at the bottom of the conduction band, which was found to be 0.27 m_e. © 2000 American Vacuum Society.

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73.61.Ga	II-VI semiconductors
71.18.+y	Fermi surface: calculations and measurements; effective mass, g factor
73.50.Dn	Low-field transport and mobility; piezoresistance
73.50.Jt	Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Lw	Thermoelectric effects

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Electrical properties of thin gate dielectric grown by rapid thermal oxidation

J. S. Lee, S. J. Chang, S. C. Sun, S. M. Jang, and M. C. Yu

J. Vac. Sci. Technol. A 18, 2986 (2000); http://dx.doi.org/10.1116/1.1312374 (6 pages) | Cited 2 times

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In this article, we adopted the rapid thermal oxidation (RTO) method to grow gate oxide layers on Si substrates. These RTO oxides were grown in both O₂ atmosphere (dry RTO oxide) and in H₂ and O₂ mixed atmosphere (wet RTO oxide) at above 1000 °C. For comparison, conventional furnace oxides were grown in H₂ and O₂ mixed atmosphere (furnace wet oxide) as the contrast samples. In this experiment, wet RTO oxides showed better electric characteristics than dry RTO oxides. We also found that a postannealing in nitric oxide (NO) atmosphere can further improve the electric properties of these wet RTO oxides. From these experimental results, we believe that postannealing in NO atmosphere is an effective method to improve oxide electric characteristics. We also found that wet RTO oxide has a superior ability to resist a constant current stress. © 2000 American Vacuum Society.

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81.65.Mq	Oxidation
73.61.Ng	Insulators

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In situ measurement of thickness dependent electrical resistance of ultrathin Co films on SiO₂/Si(111) substrate

M. Li, Y.-P. Zhao, and G.-C. Wang

J. Vac. Sci. Technol. A 18, 2992 (2000); http://dx.doi.org/10.1116/1.1314390 (5 pages) | Cited 3 times

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Ultrathin Co films of thicknesses from 1 to 19 monolayers (ML) were grown on native oxide covered Si(111) surfaces near room temperature by thermal evaporations in ultrahigh vacuum. The thickness dependent total electrical sheet resistance R (Ω/□) at room temperature was measured in situ by a four-point probe. The total sheet resistance as a function of thickness first increased and then decreased suggesting that the Co film morphology changed from discontinuous islands of 1 or 2 ML thick to continuous films for thickness d>3 ML. The sheet resistance R_Co of Co was extracted from the total sheet resistance assuming that the Co and SiO₂/Si are two parallel resistors. The value of R_Co gradually levels off to 31.5 (Ω/□) which corresponds to resistivity of 10.5 μΩ cm at ∼ 19 ML. The thickness dependent resistivity was fitted by models including surface, interface, grain boundary scatterings, and surface roughness. The surface roughness obtained from atomic force microscopy is consistent with that used in Namba's model to improve the fit of resistivity in a few ML thick regime. © 2000 American Vacuum Society.

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73.61.At	Metal and metallic alloys
81.05.Bx	Metals, semimetals, and alloys
68.55.-a	Thin film structure and morphology
73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.B-	Structure of clean surfaces (and surface reconstruction)
72.10.Fk	Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.25.+i	Surface conductivity and carrier phenomena
61.72.Mm	Grain and twin boundaries
72.15.Eb	Electrical and thermal conduction in crystalline metals and alloys
73.50.Bk	General theory, scattering mechanisms

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Study of chemical vapor deposition diamond film evolution from a nanodiamond precursor by C¹³ isotopic labeling and ion implantation

I. Gouzman, V. Richter, S. Rotter, and A. Hoffman

J. Vac. Sci. Technol. A 18, 2997 (2000); http://dx.doi.org/10.1116/1.1319677 (7 pages) | Cited 1 time

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High nucleation densities and short incubation times of polycrystalline diamond films can be promoted by the dc-glow discharge–surface interaction process as in situ surface pretreatment method. As a result of the pretreatment, a carbon nanophase film whose properties are strongly affected by the dc-glow discharge deposition parameters is formed. At optimal conditions this nanophase has a predominant diamond character which promotes diamond growth in the subsequent chemical vapor deposition (CVD) process. In this work, the evolution of the diamond film during a standard hot filament (HF) CVD process, following the dc-glow discharge pretreatment, was studied by nonreactive ion implantation of the precursor film and C¹³ isotopic labeling during different deposition stages in addition to spectroscopic and high resolution scanning electron microscopic (HR-SEM) techniques. Our results indicate that only part of the diamond growth centers formed by the dc-glow discharge process are placed on the surface but rather they are distributed homogeneously within the precursor film. Using ¹³CH₄- isotopic labeling it was shown that the nanodiamond films formed by the dc-glow discharge process are stable under standard HF CVD conditions. Only a fraction of the nanodiamond particles deposited by the dc-glow discharge processes serve as nucleation centers for the growth of diamond. A complex interlayer composed of a nanodiamond composite is formed between the silicon substrate and the microcrystalline diamond film. © 2000 American Vacuum Society.

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81.05.ub	Fullerenes and related materials
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.up	Other materials
81.05.Cy	Elemental semiconductors
81.65.-b	Surface treatments
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition

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Postdeposition annealing of pulsed laser deposited CN_x films

P. González, R. Soto, F. Lusquiños, B. León, and M. Pérez-Amor

J. Vac. Sci. Technol. A 18, 3004 (2000); http://dx.doi.org/10.1116/1.1312372 (4 pages) | Cited 3 times

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A study on the modification of the physicochemical properties of the carbon–nitrogen compounds when submitted to a thermal annealing process is reported. Original films were obtained by ArF laser ablation using organic and inorganic targets in a reactive atmosphere of ammonia or in vacuum conditions. The evolution of the film chemical composition and bonding configuration was followed by controlled thermal effusion, Fourier-transform infrared and energy dispersive x-ray spectroscopies. The thermal energy supplied to the material during the postdeposition annealing of the CN_x films promotes the formation of single CN bonds although the film nitrogen concentration decreases by the effusion of hydrogen cyanide, cyanogen, and CN radicals. Additional experiments at different substrate processing temperatures were carried out in order to analyze the role of the temperature on the film properties during the film processing and during postdeposition annealing. © 2000 American Vacuum Society.

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81.15.Fg	Pulsed laser ablation deposition
68.55.Nq	Composition and phase identification
78.30.Hv	Other nonmetallic inorganics
78.66.Nk	Insulators

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BROWSE VOLUMES

Nov 2000

Volume 18, Issue 6, pp. 2619-3013

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