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Atomic-level robustness of the Si(100)-2×1:H surface following liquid phase chemical treatments in atmospheric pressure environments

A. S. Baluch, N. P. Guisinger, R. Basu, E. T. Foley, and M. C. Hersam

J. Vac. Sci. Technol. A 22, L1 (2004); http://dx.doi.org/10.1116/1.1722203 (5 pages) | Cited 7 times

Online Publication Date: 4 May 2004

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The UHV-prepared Si(100)-2×1:H surface is studied at atomic resolution following liquid phase chemical processing under atmospheric pressure conditions. A custom experimental setup, consisting of an UHV scanning tunneling microscope (STM) chamber that is directly interfaced to an inert atmosphere glovebox, facilitates liquid phase chemical processing without exposing the pristine H-passivated surface to ambient air. While in the inert atmosphere, the Si(100)-2×1:H surface is treated with a variety of organic and aqueous solvents. Atomic resolution STM images reveal that the hydrogen passivation remains largely intact after treatments in toluene and dichloromethane. In addition, by minimizing oxygen levels during processing, perturbation to the Si(100)-2×1:H surface can be significantly reduced following exposure to water. These results are potentially useful in the fields of microelectronics and molecular-beam epitaxy, where liquid phase chemical processing is often avoided in an effort to preserve atomically pristine Si(100) surfaces. Furthermore, this study delineates the conditions under which various organic and biological molecules can be delivered to nanopatterned Si(100)-2×1:H surfaces via liquid phase solvents. © 2004 American Vacuum Society.

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81.05.Cy	Elemental semiconductors
81.65.Rv	Passivation
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces

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Effect of N₂ plasma on yttrium oxide and yttrium–oxynitride dielectrics

D. Niu, R. W. Ashcraft, C. Hinkle, and G. N. Parsons

J. Vac. Sci. Technol. A 22, 445 (2004); http://dx.doi.org/10.1116/1.1666880 (7 pages) | Cited 3 times

Online Publication Date: 9 March 2004

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In this article, we report the effect of nitrogen plasma, during and after deposition, on nitrogen incorporation into yttrium oxide dielectric films. Films are deposited using a yttrium β-diketonate precursor (Y(tmhd)₃) introduced downstream from a O₂ or N₂ plasma. The precursor acted as a significant source of oxygen, and only small amounts of N (<10 at. %) were incorporated in the films. Chemical bonding, concentration, and distribution of N in Y-oxide films after deposition and after high-temperature anneal were characterized using x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Auger electron spectroscopy. CN is the primary form of nitrogen bonding in the as-deposited films, and IR results indicate the exchange of N with O to form CO bonds occurs during prolonged exposure to air. High-temperature annealing releases N from the surface of as-deposited films, and results in a film structure that is resistant to further N incorporation. Results suggest that yttrium oxynitride is likely inherently unstable, especially in contact with ambient moisture. © 2004 American Vacuum Society.

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77.55.-g	Dielectric thin films
52.77.Dq	Plasma-based ion implantation and deposition
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

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Forced convection magnetoelectroplating for enhanced semiconductor metallization

R. A. Said

J. Vac. Sci. Technol. A 22, 452 (2004); http://dx.doi.org/10.1116/1.1666881 (9 pages) | Cited 1 time

Online Publication Date: 19 March 2004

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An efficient method that controls the rate and characteristics of copper electroplating for semiconductor metallization is demonstrated. Unlike typical electroplating processes, the proposed method operates with a forced flow of the electrolyte in the presence of an externally applied magnetic field, hence inducing a Lorentzian force that enhances the transport of depositing ions toward deposition regions. The magnitude of the induced force has been estimated to be at least one order of magnitude larger than other forces encountered in electroplating processes. A constructed experimental setup is described and used to demonstrate and investigate effects of induced Lorentzian forces on the rate and formation characteristics of deposited copper metallization. The obtained experimental results clearly demonstrate the technical and economical impact of the method in terms of providing a compact (low porosity) deposit with thin sidewalls and reducing the required deposition time by controlling the intensity of the applied magnetic field and the electrolyte flow velocity. The method holds promise for related metallization issues. © 2004 American Vacuum Society.

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81.15.Pq	Electrodeposition, electroplating
82.45.Qr	Electrodeposition and electrodissolution
85.40.Ls	Metallization, contacts, interconnects; device isolation
82.45.Gj	Electrolytes

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Chemical-beam deposition of GaN films on Si(111) from diethylazidogallium methylhydrazine adduct

Myung M. Sung, Chang G. Kim, and Yunsoo Kim

J. Vac. Sci. Technol. A 22, 461 (2004); http://dx.doi.org/10.1116/1.1666882 (4 pages) | Cited 1 time

Online Publication Date: 5 April 2004

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GaN films were grown on Si(111) substrates at 400–800 °C using a single precursor diethylazidogallium methylhydrazine adduct, Et₂(N₃)Ga⋅MeHNNH₂, under high-vacuum conditions (5×10⁻⁶ Torr). The chemical composition, crystalline structure, and morphology of the deposited films were investigated by x-ray photoelectron spectroscopy, x-ray diffraction, double crystal x-ray diffraction, x-ray pole figure analysis, and scanning electron microscopy. The results show that high-quality h-GaN films with correct stoichiometry can be deposited on Si(111) at a relatively low temperature by chemical-beam deposition (CBD). Room-temperature photoluminescence measurements have been performed to evaluate the optical properties of the GaN films. The single precursor Et₂(N₃)Ga⋅MeHNNH₂ has been found suitable for the CBD of GaN thin films on Si substrates. © 2004 American Vacuum Society.

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81.15.Hi	Molecular, atomic, ion, and chemical beam epitaxy
82.80.-d	Chemical analysis and related physical methods of analysis
61.66.Fn	Inorganic compounds
78.55.Cr	III-V semiconductors
78.66.Fd	III-V semiconductors

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Effects of thermal annealing of W/SiO₂ multilayer Bragg reflectors on resonance characteristics of film bulk acoustic resonator devices with cobalt electrodes

Munhyuk Yim, Dong-Hyun Kim, Dongkyu Chai, and Giwan Yoon

J. Vac. Sci. Technol. A 22, 465 (2004); http://dx.doi.org/10.1116/1.1690248 (7 pages) | Cited 5 times

Online Publication Date: 5 April 2004

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In this article, we present the thermal annealing effects of the W/SiO₂ multilayer reflectors in ZnO-based film bulk acoustic resonator (FBAR) devices with cobalt (Co) electrodes in comparison with those with aluminum (Al) electrodes. Various thermal annealing conditions have been implemented on the W/SiO₂ multilayer reflectors formed on p-type (100) silicon substrates. The resonance characteristics could be significantly improved due to the thermal annealing and were observed to depend strongly on the annealing conditions applied to the reflectors. Particularly, the FBAR devices with the W/SiO₂ multilayer reflectors annealed at 400 °C/30 min have shown superior resonance characteristics in terms of return loss and quality factor. In addition, the use of Co electrodes has resulted in the further improvement of the resonance characteristics as compared with the Al electrodes. As a result, the combined use of both the thermal annealing and Co electrodes seems very useful to more effectively improve the resonance characteristics of the FBAR devices with the W/SiO₂ multilayer reflectors. © 2004 American Vacuum Society.

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43.58.-e	Acoustical measurements and instrumentation
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
43.20.Ks	Standing waves, resonance, normal modes

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Cathode glow polymerization of trimethylsilane

Hirotsugu Yasuda and Qingsong Yu

J. Vac. Sci. Technol. A 22, 472 (2004); http://dx.doi.org/10.1116/1.1690776 (5 pages) | Cited 3 times

Online Publication Date: 12 April 2004

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In glow discharges of Ar, negative glow develops away from the cathode and constitutes the most luminous gas phase, and the cathode remains in the dark, i.e., there is no cathode glow. The location of negative glow is where the maximum value of electron temperature is observed, indicating that the energy of photon-emitting species is in the vicinity of ionization of the atoms involved. In glow discharges of trimethylsilane, cathode glow, the primary glow of glow discharge, appears on the cathode surface that is caused by dissociation reactions of organic molecules upon low-energy electron impact, which can be more properly termed molecular dissociation glow. Dissociation glow develops at the very onset in various glow discharges and, at that stage, negative glow is barely visible, but becomes visible as the gas phase composition changes due to plasma polymerization, which deposits polymerizable species into solid thin films and leaves nonpolymerizable species such as hydrogen atoms and molecules in the gas phase. Dissociation glow is not observed with simple molecular gases such as O₂, N₂, and CO₂, which do not deposit material. © 2004 American Vacuum Society.

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82.45.Fk	Electrodes
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
82.35.-x	Polymers: properties; reactions; polymerization
82.45.Wx	Polymers and organic materials in electrochemistry
34.80.Ht	Dissociation and dissociative attachment
52.80.Hc	Glow; corona

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Ionized magnetron sputter deposition of hard nanocomposite TiN/amorphous-silicon nitride films

N. Phinichka, R. Chandra, and Z. H. Barber

J. Vac. Sci. Technol. A 22, 477 (2004); http://dx.doi.org/10.1116/1.1690778 (5 pages) | Cited 6 times

Online Publication Date: 12 April 2004

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Thin films of Ti–Si–N have been deposited by ionized magnetron sputter deposition using separate Ti and Si targets in an Ar/N₂ gas mixture. A built-in rf coil generated an inductively coupled plasma close to the substrate. With this setup, the ion flux and energy can be controlled by adjusting the rf power to the coil and the dc substrate bias. Deposition was carried out under various conditions to investigate the effects of different operational parameters on film structure and mechanical properties. Crystallography, grain size, and film texture have been characterized by x-ray diffraction, showing that the addition of Si to TiN films transforms the (111)-oriented structure to a preferred (200)-oriented structure. The nanocrystallite domain size of the TiN, calculated from peak broadening, was found to be less than 10 nm. No signals from crystalline Si₃N₄ or other phases of titanium silicide were observed. The hardness of the films, measured using nanoindentation, increased to as much as twice that of pure TiN films. © 2004 American Vacuum Society.

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81.15.Cd	Deposition by sputtering
68.55.-a	Thin film structure and morphology
62.20.M-	Structural failure of materials
81.07.Bc	Nanocrystalline materials
61.43.-j	Disordered solids
62.20.Qp	Friction, tribology, and hardness
68.35.Gy	Mechanical properties; surface strains
68.60.Bs	Mechanical and acoustical properties

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Thickness measurements by quartz microbalance during thin-film growth by organic-molecular-beam deposition

M. Campione, M. Cartotti, E. Pinotti, A. Sassella, and A. Borghesi

J. Vac. Sci. Technol. A 22, 482 (2004); http://dx.doi.org/10.1116/1.1690249 (5 pages) | Cited 11 times

Online Publication Date: 12 April 2004

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The problem of in situ monitoring the film thickness by quartz microbalance during vacuum deposition of organic-molecular semiconductors is addressed herein by setting a procedure for sensor calibration based on ex situ analysis of the deposited molecular film by atomic-force microscopy measurements. The procedure is applied to the growth of molecular-organic thin films on silica. Some physical parameters of the materials are deduced. © 2004 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
06.30.Bp	Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
81.15.-z	Methods of deposition of films and coatings; film growth and epitaxy

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Hydrogenated-amorphous carbon nitride films formed from the dissociative excitation reaction of CH₃CN with the microwave-discharge flow of Ar: Correlation of the [N]/([N]+[C]) ratio with the relative number densities of the CH(A²Δ) and CN(B²Σ⁺) states

Haruhiko Ito, Hiroshi Miki, Kei-ichi C. Namiki, Noriko Ito, Hidetoshi Saitoh, Tsuneo Suzuki, and Kiyoshi Yatsui

J. Vac. Sci. Technol. A 22, 487 (2004); http://dx.doi.org/10.1116/1.1690250 (7 pages) | Cited 5 times

Online Publication Date: 12 April 2004

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High-resolution optical emission spectra of the CN(B²Σ⁺–X²Σ⁺) and CH(A²Δ–X²Π) transitions were observed in the dissociative excitation reaction of CH₃CN with the microwave-discharge flow of Ar. The H₂O molecules contained in the starting materials and/or adsorbed on the wall of the apparatus were removed by using P₂O₅ as a desiccant. The pressure of Ar, P_Ar, was in the range of 0.1–0.8 Torr. From the simulation analysis of the observed spectra, the ratio of the concentrations of the CH(A²Δ) and CN(B²Σ⁺) states, N_CH(A)/N_CN(B), was determined as 0.09–0.41. It was indicated that the CN(B²Σ⁺) state was formed via the ion–electron recombination as well as the energy transfer from the metastable state of Ar. Based on the correlation between the N_CH(A)/N_CN(B) and [N]/([N]+[C]) ratios reported in the system without desiccation [Jpn. J. Appl. Phys. 40, 332 (2001)], the [N]/([N]+[C]) ratio in the desiccated system was predicted to be ≈0.18. The hydrogenated-amorphous carbon nitride films prepared under the conditions of P_Ar=0.1, 0.4, 0.6, and 0.8 Torr were characterized by the Rutherford backscattering (RBS) analysis and the Fourier transform infrared (FTIR) spectroscopy. The observed [N]/([N]+[C]) ratios of the films were in the range of 0.17–0.21, being in good agreement with the above prediction. The structure of the films was independent of P_Ar. The observed correlation between the N_CH(A)/N_CN(B) and [N]/([N]+[C]) ratios can be rationalized by the consideration that the relative concentrations of the CH(A²Δ) and CN(B²Σ⁺) states and those of the precursor free radicals of the films are supposed to originate commonly to the relative concentrations of the active species of the discharge flow of Ar. © 2004 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
78.30.-j	Infrared and Raman spectra
78.66.-w	Optical properties of specific thin films
82.30.Lp	Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.80.Yc	Rutherford backscattering (RBS), and other methods of chemical analysis
82.30.Fi	Ion-molecule, ion-ion, and charge-transfer reactions
82.30.Nr	Association, addition, insertion, cluster formation
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
52.77.Dq	Plasma-based ion implantation and deposition
81.15.Jj	Ion and electron beam-assisted deposition; ion plating

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Effect of deposition temperature on thermal stability in high-density plasma chemical vapor deposition fluorine-doped silicon dioxide

Y. L. Cheng, Y. L. Wang, H. W. Chen, J. L. Lan, C. P. Liu, S. A. Wu, Y. L. Wu, K. Y. Lo, and M. S. Feng

J. Vac. Sci. Technol. A 22, 494 (2004); http://dx.doi.org/10.1116/1.1690779 (6 pages) | Cited 2 times

Online Publication Date: 14 April 2004

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Thermal stability of fluorine-doped silicon dioxide films deposited by high-density plasma chemical vapor deposition as a function of deposition temperature were investigated in this study. Both thermal desorption spectrum and annealing test results show that SiOF films deposited above 400 °C have better thermal stability. Furnace annealing data indicate that non �Si�F� bonding fluorine does exist in low-deposition-temperature SiOF films. Furthermore, secondary-ion mass spectrometer results also reveal that the fluorine in SiOF films with a lower-deposition temperature is easily diffused out and turned into the underlayer, which results in less thermally stable SiOF films. Moreover, short-loop simulation results have been subsequently tested and it was concluded that the deposition temperature of the SiOF film is extremely important for thermal stability. © 2004 American Vacuum Society.

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68.60.Dv	Thermal stability; thermal effects
68.60.Wm	Other nonelectronic physical properties
79.20.Rf	Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms	Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Gh	Other heat and thermomechanical treatments
68.43.Mn	Adsorption kinetics
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

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Properties of C₄F₈ inductively coupled plasmas. I. Studies of Ar/c-C₄F₈ magnetically confined plasmas for etching of SiO₂

Xi Li, Li Ling, Xuefeng Hua, Gottlieb S. Oehrlein, Yicheng Wang, Alex V. Vasenkov, and Mark J. Kushner

J. Vac. Sci. Technol. A 22, 500 (2004); http://dx.doi.org/10.1116/1.1697482 (11 pages) | Cited 16 times

Online Publication Date: 27 April 2004

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Gas mixtures containing c-C₄F₈/Ar are commonly used for the plasma etching of dielectric materials such as SiO₂. To quantify the dependence of fundamental plasma parameters of systems using these mixtures, inductively coupled plasmas in the pressure range of 6–20 mTorr, with and without magnetic confinement, were investigated. Measurements were also made in pure Ar and O₂ to provide a comparison baseline. We found that use of magnetic confinement strongly influences the total ion flux, ion composition, and ion energy distributions in these discharges. Magnetic confinement increases the ion saturation current density, as measured with a Langmuir probe, most effectively at the lowest pressure examined here (6 mTorr). The increase in current density generally decreases as the pressure increases. Mass spectroscopic measurements of the ion flux showed that the CF⁺ ion flux dominates in C₄F₈ discharges, both with and without magnetic confinement. When Ar is added to C₄F₈ discharges with magnetic confinement, the CF2+ and CF3+ ion fluxes increase, and CF3+ becomes the dominant fluorocarbon ion. The ion energy distributions with and without magnetic field indicate that the plasma potential is generally lower for the magnetically confined discharges, although these trends are not monotonic when diluting C₄F₈ with Ar. Etching rates of SiO₂, Si, and photoresist are higher with magnetic confinement, while etching yields are lower. The chemical compositions of passively deposited fluorocarbon films on Si, as measured by x-ray photoemission spectroscopy, differ little with and without magnetic confinement for varying C₄F₈/Ar gas compositions. © 2004 American Vacuum Society.

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52.70.Ds	Electric and magnetic measurements
52.55.-s	Magnetic confinement and equilibrium
52.77.Bn	Etching and cleaning

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Properties of c-C₄F₈ inductively coupled plasmas. II. Plasma chemistry and reaction mechanism for modeling of Ar/c-C₄F₈/O₂ discharges

Alex V. Vasenkov, Xi Li, Gottlieb S. Oehrlein, and Mark J. Kushner

J. Vac. Sci. Technol. A 22, 511 (2004); http://dx.doi.org/10.1116/1.1697483 (20 pages) | Cited 28 times

Online Publication Date: 27 April 2004

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Gas mixtures containing Ar, c-C₄F₈, O₂, and CO are often used for the plasma etching of silicon dioxide. Gas phase reaction mechanisms are required for first principles modeling of these systems to both provide insights to the plasma chemistry and to help optimize the process. In this article, results from computational and experimental investigations of the plasma chemistry of inductively coupled plasmas (ICPs) sustained in Ar, O₂, Ar/c-C₄F₈ and O₂/c-C₄F₈ gas mixtures with and without magnetic confinement are discussed. These results were used to develop a reaction mechanism for low-pressure and low-temperature plasmas sustained in mixtures initially consisting of any combination of Ar/c-C₄F₈/O₂/CO. Predictions for ion saturation current and ion mass fractions were compared to experiments for validation. The consequences of charge exchange of fluorocarbon species with Ar⁺ and CO⁺ on the ratio of light to heavy fluorocarbon ion densities in Ar/c-C₄F₈/O₂/CO plasmas are discussed. We found that the electron density and ion saturation current significantly increase with the addition of Ar to c-C₄F₈ but weakly depend on the addition of O₂. The ratio of light to heavy fluorocarbon ion densities increases with power, especially for ICPs with magnetic confinement. © 2004 American Vacuum Society.

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52.25.-b	Plasma properties
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
52.55.-s	Magnetic confinement and equilibrium
52.80.Dy	Low-field and Townsend discharges
82.30.Fi	Ion-molecule, ion-ion, and charge-transfer reactions

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Electron-cyclotron-resonance plasma etching of the ZnO layers grown by molecular-beam epitaxy

K. Ogata, T. Honden, T. Tanite, T. Komuro, K. Koike, S. Sasa, M. Inoue, and M. Yano

J. Vac. Sci. Technol. A 22, 531 (2004); http://dx.doi.org/10.1116/1.1690777 (3 pages) | Cited 7 times

Online Publication Date: 27 April 2004

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Etching of high-quality ZnO layers grown by molecular-beam epitaxy was examined by using electron-cyclotron-resonance plasma etching. Etching rates of ZnO layers were larger using CH₄ than CF₄, and four times more enhanced by using a mixture of the two gases. For a ZnO surface covered with photoresist layers by the plasma-etching procedure, degradation was mostly recovered by thermal annealing in an O₂ atmosphere at the proper temperatures. This was found to be effective for the recovery of the layers. © 2004 American Vacuum Society.

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81.05.Dz	II-VI semiconductors
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Gh	Other heat and thermomechanical treatments
68.55.-a	Thin film structure and morphology
81.15.Hi	Molecular, atomic, ion, and chemical beam epitaxy
52.77.Bn	Etching and cleaning
81.65.Cf	Surface cleaning, etching, patterning
78.60.Hk	Cathodoluminescence, ionoluminescence
68.47.Fg	Semiconductor surfaces
78.55.Et	II-VI semiconductors
78.66.Hf	II-VI semiconductors

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Extraction of negative ions from pulsed electronegative inductively coupled plasmas having a radio-frequency substrate bias

Pramod Subramonium and Mark J. Kushner

J. Vac. Sci. Technol. A 22, 534 (2004); http://dx.doi.org/10.1116/1.1690251 (11 pages) | Cited 5 times

Online Publication Date: 27 April 2004

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Pulsed electronegative plasmas are promising candidates for reducing charge buildup during microelectronics fabrication by extracting negative ions into features. By modulating power in inductively coupled plasmas (ICPs), the plasma potential collapses during the power-off period, thereby allowing negative ions to be extracted. In principle, application of a radio-frequency (rf) substrate bias should accelerate these ions into features. In practice, this goal is not always achieved due to the unfavorable dynamics of the plasma potential. We computationally investigated the extraction of negative ions in the afterglow of pulsed ICPs having rf substrate biases sustained in Ar/Cl₂ gas mixtures. We found that the extraction of negative ions is optimized by delaying the transition to a capacitive heating mode in the afterglow, which can be achieved by the addition of Ar to Cl₂ plasmas. Increasing the bias voltage causes a capacitive heating mode to begin earlier, which prevents negative ions from being extracted. To circumvent this effect, schemes were investigated in which the rf bias is applied for only a portion of the pulse period. At high rf frequencies (≈10 MHz), ions striking the substrate have only thermal energies due to the majority of the applied bias being dropped across the bulk plasma. At lower frequencies (≈2 MHz), negative ions with 2–25 eV energy were extracted with an anisotropic angular distribution due to more favorable sheath formation. © 2004 American Vacuum Society.

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52.80.Hc	Glow; corona
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
52.80.Pi	High-frequency and RF discharges
52.40.Kh	Plasma sheaths
52.50.Qt	Plasma heating by radio-frequency fields; ICR, ICP, helicons

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Numerical simulation of the thermal-mechanical process of high current pulsed electron beam treatment

Jianxin Zou, Ying Qin, Chuang Dong, Xiaogang Wang, Aimin Wu, and Shengzhi Hao

J. Vac. Sci. Technol. A 22, 545 (2004); http://dx.doi.org/10.1116/1.1697481 (8 pages) | Cited 25 times

Online Publication Date: 27 April 2004

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Physical models and numerical simulations are used to describe the thermal-mechanical process induced by high current pulsed electron beam (energy E=10–40 keV, energy density in a pulse S=1–6 J/cm², pulse duration τ=0.5–5 μs) irradiation. The temperature simulation reveals ultrahigh heating and cooling rates on the order of 10⁸–10⁹ K/s, rapid melting and re-solidification within microseconds in the range of micrometers in depth, and evaporation of the surface material. The temperature-induced nonstationary thermal stress fields consist mainly of quasistatic stress and thermal stress waves. The thermal stress wave is a typical nonlinear wave with small amplitudes of about 0.1 MPa, which manifests, however, a strong impact on materials structure and properties far beyond the heat-affected zone. The quasistatic stress is coupled with the temperature field and the maximum compressive stress in the near surface layer reaches several hundreds of MPa, which is sufficiently high for metallic materials to deform. According to the calculation and experimental results, the strengthening mechanism of metals under the thermal impact is suggested to be the work-hardening with high deformation rates, which reach about 10⁴–10⁵ s⁻¹. © 2004 American Vacuum Society.

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62.20.F-	Deformation and plasticity
81.40.Lm	Deformation, plasticity, and creep
61.82.Bg	Metals and alloys
64.70.F-	Liquid-vapor transitions
64.70.D-	Solid-liquid transitions
81.30.Fb	Solidification
61.80.Fe	Electron and positron radiation effects
81.40.Gh	Other heat and thermomechanical treatments
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

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Monitoring chamber walls coating deposited during plasma processes: Application to silicon gate etch processes

O. Joubert, G. Cunge, B. Pelissier, L. Vallier, M. Kogelschatz, and E. Pargon

J. Vac. Sci. Technol. A 22, 553 (2004); http://dx.doi.org/10.1116/1.1697484 (11 pages) | Cited 26 times

Online Publication Date: 27 April 2004

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During plasma etching processes, organic or mineral layers are deposited on the chamber walls. In general, these layers cause large and uncontrolled shifts in the etch process, which is becoming a major issue in some of the plasma processes used in integrated circuit fabrication. The chemical nature of these layers and their deposition mechanisms remain poorly understood due to the lack of in situ surface diagnostics available to monitor the reactor walls. In this article, we present a simple technique using x-ray photoelectron spectroscopy (XPS) analyses to monitor the chemical composition of the layer deposited on a sample floating on top of a 200-mm-diam wafer where the layers deposited are identical to those deposited on the chamber walls. The principle of the technique is to stick a small Al₂O₃ sample onto the 200-mm-diam silicon wafer, with an air gap between the sample and the wafer. Providing that the air gap is thick enough, the Al₂O₃ surface will be electrically floating even when the silicon wafer is rf biased. During the etching process, the Al₂O₃ sample thus experiences exactly the same plasma conditions as the reactor walls. As the sample is physically clamped on the wafer, it can then be transferred under vacuum to an XPS analyzer, allowing quasi-in situ analyses of the deposited layers. The validity of the technique has been tested during silicon gate etching in HBr/Cl₂/O₂ plasmas, which are known to deposit silicon oxychloride layers on the chamber walls. The influence of CF₄ addition in the plasma which has been recently introduced in gate etching manufacturing is also analyzed using the same technique. In a second step, we show that the presence of photoresist on the etched wafer profoundly affects the chemical nature of the layers formed on the chamber walls, mainly by significantly increasing the carbon concentration in the deposited layer. © 2004 American Vacuum Society.

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52.77.Bn	Etching and cleaning
81.65.Cf	Surface cleaning, etching, patterning
79.60.Bm	Clean metal, semiconductor, and insulator surfaces
81.05.Cy	Elemental semiconductors

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Effects of germanium content on sol-gel GeO₂/γ-glycidoxypropyltrimethoxysilane hybrid planar waveguides prepared at low temperature

Wenxiu Que and X. Hu

J. Vac. Sci. Technol. A 22, 564 (2004); http://dx.doi.org/10.1116/1.1697485 (6 pages)

Online Publication Date: 27 April 2004

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The effects of germanium content on the structural and optical properties of GeO₂/γ-glycidoxypropyltri-methoxysilane hybrid materials processed by the sol-gel technique are studied for optical waveguide applications. Glass planar waveguide thin films with thickness of more than 2.0 μm are prepared by a single-coating process and low-temperature heat treatment from this high germanium content hybrid material. Multimode light guiding is demonstrated in the hybrid planar waveguide films. The properties of the planar waveguide films such as refractive index, thickness, and transparency as well as structural characterization using the prism coupling technique, atomic force microscopy, thermal gravimetric analysis, UV-visible spectroscopy, and Fourier transform infrared spectroscopy, are systematically studied. These results indicate that the refractive index increases and film thickness decreases with an increase in GeO₂ content, and thus dense, low absorption, and high transparency in the visible range waveguide films can be obtained at a low temperature. Waveguide propagation characteristics, at 632.8 and 1550 nm, are studied. The propagation loss of the hybrid waveguide film with a GeO₂ content of 0.3 M is measured to be 1.2 dB/cm at the wavelength of 1550 nm. © 2004 American Vacuum Society.

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42.79.Gn	Optical waveguides and couplers
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

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Composition, structural, and electrical properties of fluorinated silicon–nitride thin films grown by remote plasma-enhanced chemical-vapor deposition from SiF₄/NH₃ mixtures

J. Fandiño, A. Ortiz, L. Rodríguez-Fernandez, and J. C. Alonso

J. Vac. Sci. Technol. A 22, 570 (2004); http://dx.doi.org/10.1116/1.1699335 (8 pages) | Cited 3 times

Online Publication Date: 27 April 2004

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Fluorinated silicon–nitride films (SiN_x:F) have been prepared at 250 °C by remote plasma-enhanced chemical-vapor deposition using mixtures of SiF₄/NH₃ in different proportions. The structure, relative composition, and fluorine content of the films were evaluated by Fourier-transform infrared spectroscopy, Rutherford backscattering, ellipsometry, and resonant nuclear-reaction analysis. The electrical properties of the films were also assessed from the current–voltage characteristics of Al–SiN_x:F–Si metal–insulating–semiconductor structures. It was found that the SiF₄/NH₃ ratio produces little influence on the refractive index and density of the films, but this ratio has important effects on the fluorine content, deposition rate, and electrical properties. In general, these SiN_x:F films are free of Si–H bonds, chemically stable, and show breakdown fields above 8 MV/cm. © 2004 American Vacuum Society.

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52.77.Dq	Plasma-based ion implantation and deposition
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Nq	Composition and phase identification
68.55.-a	Thin film structure and morphology
77.55.-g	Dielectric thin films
78.30.Am	Elemental semiconductors and insulators
73.61.Ng	Insulators
73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Jp	Dielectric breakdown and space-charge effects
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
82.80.-d	Chemical analysis and related physical methods of analysis
77.84.Bw	Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

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Effects of atomic hydrogen on the selective area growth of Si and Si_1−xGe_x thin films on Si and SiO₂ surfaces: Inhibition, nucleation, and growth

T. W. Schroeder, A. M. Lam, P. F. Ma, and J. R. Engstrom

J. Vac. Sci. Technol. A 22, 578 (2004); http://dx.doi.org/10.1116/1.1699336 (16 pages) | Cited 3 times

Online Publication Date: 27 April 2004

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Supersonic molecular beam techniques have been used to study the nucleation of Si and Si_1−xGe_x thin films on Si and SiO₂ surfaces, where Si₂H₆ and GeH₄ have been used as sources. A particular emphasis of this study has been an examination of the effects of a coincident flux of atomic hydrogen. The time associated with formation of stable islands of Si or Si_1−xGe_x on SiO₂ surfaces—the incubation time—has been found to depend strongly on the kinetic energy of the incident molecular precursors (Si₂H₆ and GeH₄) and the substrate temperature. After coalescence, thin film morphology has been found to depend primarily on substrate temperature, with smoother films being grown at substrate temperatures below 600 °C. Introduction of a coincident flux of atomic hydrogen has a large effect on the nucleation and growth process. First, the incubation time in the presence of atomic hydrogen has been found to increase, especially at substrate temperatures below 630 °C, suggesting that hydrogen atoms adsorbed on Si-like sites on SiO₂ can effectively block nucleation of Si. Unfortunately, in terms of promoting selective area growth, coincident atomic hydrogen also decreases the rate of epitaxial growth rate, essentially offsetting any increase in the incubation time for growth on SiO₂. Concerning Si_1−xGe_x growth, the introduction of GeH₄ produces substantial changes in both thin film morphology and the rate nucleation of poly-Si_1−xGe_x on SiO₂. Briefly, the addition of Ge increases the incubation time, while it lessens the effect of coincident hydrogen on the incubation time. Finally, a comparison of the maximum island density, the time to reach this density, and the steady-state polycrystalline growth rate strongly suggests that all thin films [Si, Si_1−xGe_x, both with and without H(g)] nucleate at special sites on the SiO₂ surface, and grow primarily via direct deposition of adatoms on pre-existing islands. © 2004 American Vacuum Society.

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68.55.A-	Nucleation and growth
68.55.-a	Thin film structure and morphology
81.15.Hi	Molecular, atomic, ion, and chemical beam epitaxy
68.43.Hn	Structure of assemblies of adsorbates (two- and three-dimensional clustering)

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In situ photoemission study of a Pr₂O₃ thin film on GaAs(111)

J. X. Wu, Z. M. Wang, S. Li, and M. S. Ma

J. Vac. Sci. Technol. A 22, 594 (2004); http://dx.doi.org/10.1116/1.1699337 (4 pages) | Cited 3 times

Online Publication Date: 27 April 2004

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A Pr₂O₃ thin film, with a thickness of about 30 Å, was grown on GaAs(111) at room temperature by depositing Pr in an oxygen ambiance. In situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy were employed to investigate the Pr₂O₃/GaAs system as a function of annealing temperature. The valence-band offset of the Pr₂O₃/GaAs interface is 1.2±0.1 eV. After Pr₂O₃ deposition, some Ga atoms are bonded to Pr at the interface. Annealing leads to the decreases in the intensity of the Pr–Ga bond and facilitates the reaction between oxygen and semiconductor surface. Interfacial oxygen, observed after annealing at 430 K, is initially bonded to As and gradually transfers to Ga forming Ga₂O₃ for further annealing. © 2004 American Vacuum Society.

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79.60.Bm	Clean metal, semiconductor, and insulator surfaces
73.20.At	Surface states, band structure, electron density of states
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
77.55.-g	Dielectric thin films
68.47.Fg	Semiconductor surfaces
78.66.Fd	III-V semiconductors
81.40.Gh	Other heat and thermomechanical treatments

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Etching mechanism of a GaN/InGaN/GaN heterostructure in Cl₂- and CH₄-based inductively coupled plasmas

H. K. Kim, H. Lin, and Y. Ra

J. Vac. Sci. Technol. A 22, 598 (2004); http://dx.doi.org/10.1116/1.1699338 (4 pages) | Cited 1 time

Online Publication Date: 27 April 2004

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The etching mechanism of a GaN/InGaN/GaN heterostructure was studied using Cl₂- and CH₄-based inductively coupled plasma. The Cl₂-based plasmas are effective for fast and smooth etching of the homogeneous GaN layer. However, when the layer has a heterogeneous structure of GaN/InGaN/GaN, Cl₂-based plasmas cause many pits or pillars on the surface due to a micromasking effect of low volatile In chlorides. The growth of pillars was accompanied by microtrenching at the bottom of each pillar, which transformed into pits after the pillars were detached from their sites. By adding CH₄ gas to the Cl₂ plasma, the formation of pillars or pits was reduced, and very smooth surface morphology was demonstrated at the gas condition of 35Cl₂+20CH₄+5Ar (sccm). © 2004 American Vacuum Society.

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52.77.Bn	Etching and cleaning
68.47.Fg	Semiconductor surfaces
81.65.Cf	Surface cleaning, etching, patterning
81.05.Ea	III-V semiconductors

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Template stripping using cold welding

Jason J. Blackstock, Zhiyong Li, and Gun-young Jung

J. Vac. Sci. Technol. A 22, 602 (2004); http://dx.doi.org/10.1116/1.1710492 (4 pages) | Cited 5 times

Online Publication Date: 27 April 2004

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A method for fabricating ultra-flat template-stripped (TS) metal surfaces on standard silicon/silicon-oxide wafers by means of gold cold-welding is presented, and cold-welded template-stripped (CWTS) platinum surfaces are demonstrated as an example. Due to the lack of any adhesives, the final TS metal “sandwiches” are fully compatible with all organic solvents, as well as ultra-high vacuum (UHV). The produced CWTS platinum surfaces are demonstrated to have the same surface properties—most importantly single-angstrom rms roughness—as previously studied TS platinum. The effectiveness of the cold-welding technique is shown to decrease as a function of time exposed to ambient laboratory conditions after removal from vacuum and prior to pressurized cold-welding. Contact angle measurements demonstrate this decrease to be due to a gradual increase in surface contamination of the evaporated gold layers prior to their being joined by cold-welding. The potential versatility and scalability of the CWTS fabrication process is briefly discussed. © 2004 American Vacuum Society.

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81.20.Vj	Joining; welding
68.35.Dv	Composition, segregation; defects and impurities

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Etching of high aspect ratio structures in Si using SF₆/O₂ plasma

Sergi Gomez, Rodolfo Jun Belen, Mark Kiehlbauch, and Eray S. Aydil

J. Vac. Sci. Technol. A 22, 606 (2004); http://dx.doi.org/10.1116/1.1710493 (10 pages) | Cited 30 times

Online Publication Date: 27 April 2004

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We have investigated etching of deep (∼10 μm) submicron diameter holes with high aspect ratios (>10) using plasmas maintained in mixtures of SF₆ and O₂ gases. The etching experiments were conducted in a low-pressure (5–80 mTorr), high-density, inductively coupled plasma etching reactor with a planar coil. We have studied the effects of pressure, rf-bias voltage, and SF₆-to-O₂ gas ratio on the etch rate, selectivity, and feature profile using Si wafers patterned with 0.35–0.5 μm diameter holes in a SiO₂ mask. Visualization of the profiles with scanning electron microscopy is used in conjunction with plasma diagnostics such as optical emission and mass spectroscopies to understand the key factors that control the anisotropy, selectivity, and etch rate. The F-to-ion flux ratio and F-to-O flux ratio are found to be the important plasma parameters that determine the etch rate and anisotropy. Increasing the SF₆-to-O₂ ratio in the feed gas increases the F-to-O ratio in the plasma. At high SF₆-to-O₂ ratio, the mask undercut is severe because sidewall passivation by O atoms cannot keep up with the chemical etching by F atoms. As the F-to-O ratio is decreased, effective sidewall passivation by O atoms results in nearly vertical sidewalls. A further reduction in the F-to-O ratio results in sidewalls that slope inwards toward the bottom of the feature. © 2004 American Vacuum Society.

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52.77.Bn	Etching and cleaning
81.65.Cf	Surface cleaning, etching, patterning
52.70.Kz	Optical (ultraviolet, visible, infrared) measurements
68.35.B-	Structure of clean surfaces (and surface reconstruction)
81.65.Rv	Passivation
68.47.Fg	Semiconductor surfaces

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Deposition of Hf–silicate gate dielectric on Si_xGe_1−x(100): Detection of interfacial layer growth

S. Addepalli, P. Sivasubramani, M. El-Bouanani, M. J. Kim, B. E. Gnade, and R. M. Wallace

J. Vac. Sci. Technol. A 22, 616 (2004); http://dx.doi.org/10.1116/1.1710494 (8 pages) | Cited 2 times

Online Publication Date: 27 April 2004

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The deposition of a stable high-κ dielectric material such as hafnium silicate in direct contact with strained epitaxial Si_xGe_1−x(100) layers on Si(100) provides the prospect of eliminating the Si buffer layer that is currently used to form the gate oxide in SiGe-based devices. In this study, ∼3-nm-thick hafnium silicate films were produced by sputter deposition of hafnium silicide films on precleaned Si_xGe_1−x(100), with subsequent UV-O₃ oxidation at room temperature. Prolonged UV-O₃ exposure at room temperature leads to the growth of an interfacial layer comprised of a mixture of silicon and germanium oxides. We report on the use of x-ray photoelectron spectroscopy, particularly the x-ray excited Ge (L₃MM) Auger feature to optimize UV-O₃ exposure time, and minimize the interfacial layer growth of silicon and germanium oxides. © 2004 American Vacuum Society.

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77.55.-g	Dielectric thin films
81.15.Cd	Deposition by sputtering
81.65.Mq	Oxidation
79.60.Bm	Clean metal, semiconductor, and insulator surfaces

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Analysis of the chemical composition and deposition mechanism of the SiO_x–Cl_y layer on the plasma chamber walls during silicon gate etching

Martin Kogelschatz, Gilles Cunge, and Nader Sadeghi

J. Vac. Sci. Technol. A 22, 624 (2004); http://dx.doi.org/10.1116/1.1710496 (12 pages) | Cited 26 times

Online Publication Date: 27 April 2004

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During silicon gate etching in low pressure high density HBr/Cl₂/O₂ plasma, SiOCl_x layers are deposited on the reactor walls. These layers are at the origin of process drifts. However their chemical composition, deposition mechanism and their influence on the plasma chemistry remains poorly understood. In this study, the chemical composition of this layer has been investigated by a “plasma etching-sputtering” technique: the silicon oxychloride layer deposited on the reactor walls during the etching of a 200 mm diam silicon wafer has been subsequently submitted to an Ar plasma with the addition of a few % SF₆. During the slow etch process of this layer, time-resolved optical emission spectroscopy and mass spectrometry have been used to follow the time evolution of the gas phase concentration of different atoms and radicals, the etch products of the SiOCl_x layer. The results give insight into the chemical nature of the deposited layer and of its variation as a function of the depth. In particular, it will be shown that these layers are chlorine-rich and not oxidelike. Also, their composition is not homogeneous through their depth. In a second set of experiments, the SiOCl_x layer has been exposed to an Ar/O₂ plasma providing information on the oxidation mechanism of the Si–Cl bonds and thus on the SiOCl_x film deposition mechanism in HBr/Cl₂/O₂ plasmas. This oxidation mechanism is acting through the entire volume of the 10 nm thick layers and proceeds by substitution of Cl atoms of SiCl bonds by O atoms, resulting in desorption of a large amount of Cl atoms from the chamber walls during the layer oxidation. Finally, the layer on the chamber walls has been exposed to an Ar/Cl₂ plasma, demonstrating that SiOCl_x layers are not etched significantly by Cl atoms. © 2004 American Vacuum Society.

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52.40.Hf	Plasma-material interactions; boundary layer effects
52.77.Bn	Etching and cleaning
81.65.Cf	Surface cleaning, etching, patterning
81.05.Cy	Elemental semiconductors
82.33.Xj	Plasma reactions (including flowing afterglow and electric discharges)
79.70.+q	Field emission, ionization, evaporation, and desorption

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Oxygen plasma rapid thermal annealing to improve the electrical properties of Pt–SrBi₂Nb₂O₉–SiO₂–Si gate structure

Ik Soo Kim, Seong-Il Kim, and Yong Tae Kim

J. Vac. Sci. Technol. A 22, 636 (2004); http://dx.doi.org/10.1116/1.1710497 (4 pages)

Online Publication Date: 27 April 2004

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A rapid thermal annealing (RTA) method in oxygen plasma improves the ferroelectric properties of SrBi₂Nb₂O₉ (SBN) film at relatively lower temperature than the conventional furnace annealing in oxygen ambient. The oxygen plasma RTA raises the oxygen content from 44 to 48 at. %, which may improve the oxygen deficiency in the SBN films. The thickness of SiO₂ becomes thinner due to the shorter RTA time. As a result, a typical effective memory window of the Pt–SBN–SiO₂–Si gate structure is increased from 0.17 to 0.49 V at 3 V of the applied gate bias and the remnant polarization is also increased from 18.03 to 22.6 C/cm² at ±6 V. The flat band voltage shift of the oxygen plasma RTA samples is quite stable and smaller than that of the furnace annealed ones because charge trapping is relatively smaller at the interface between Si and the oxygen plasma annealed SBN film. © 2004 American Vacuum Society.

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77.80.-e	Ferroelectricity and antiferroelectricity
73.20.-r	Electron states at surfaces and interfaces
61.72.Cc	Kinetics of defect formation and annealing
77.55.-g	Dielectric thin films

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SiBCN synthesis by high-dose N⁺+C⁺+BF2+ ion implantation

M. Cervera, M. J. Hernández, J. Piqueras, C. Morant, P. Prieto, E. Elizalde, and J. M. Sanz

J. Vac. Sci. Technol. A 22, 640 (2004); http://dx.doi.org/10.1116/1.1710498 (6 pages) | Cited 4 times

Online Publication Date: 27 April 2004

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High-dose implantation processes of N⁺+C⁺+BF2+ have been performed on Si(100) substrates at 600 °C. Additional simple (N⁺,C⁺) and double (N⁺+C⁺ and N⁺+BF2+) implantations have also been produced to sequentially study the synthesis of different semiconductor compounds. FTIR spectra of all the samples before and after thermal annealing at 1200 °C have been acquired. When N⁺ and C⁺ are co-implanted the formation of a ternary phase of SiCN nature is suggested, meanwhile in the case of N⁺ and BF2+ competition between BN and Si₃N₄ takes place. The sequential implantation of the three species produces a stable surface region as deduced from the AES profiles. IR and XPS measurements suggest the formation of a SiCB_xN_y mainly formed by SiC with a significant content of B and N (∼20%). © 2004 American Vacuum Society.

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61.72.up	Other materials
61.80.Jh	Ion radiation effects
61.82.Fk	Semiconductors
68.49.Jk	Electron scattering from surfaces
79.20.Fv	Electron impact: Auger emission
79.60.Bm	Clean metal, semiconductor, and insulator surfaces
61.72.Cc	Kinetics of defect formation and annealing
81.40.Gh	Other heat and thermomechanical treatments

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Physical and mechanical properties of sputtered Ta–Si–N films with a high (⩾40 at %) content of Si

H. Zeman, J. Musil, and P. Zeman

J. Vac. Sci. Technol. A 22, 646 (2004); http://dx.doi.org/10.1116/1.1710499 (4 pages) | Cited 9 times

Online Publication Date: 27 April 2004

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This article reports on ternary Ta–Si–N films with a high (⩾40 at %) content of Si sputtered from an alloyed TaSi₂ target using an unbalanced dc magnetron. The films were deposited under the following conditions: magnetron discharge current I_d=1 and 2 A, negative substrate bias U_s ranging from U_fl to −500 V, substrate ion current density i_s=0.5, 0.75, and 1 mA/cm², substrate temperature T_s ranging from 100 to 750 °C, substrate-to-target distance d_s–t=60 mm, partial pressure of nitrogen p_N2 ranging from 0 to 0.7 Pa and two values of a total pressure p_T=p_Ar+p_N2=0.5 and 0.7 Pa. Main attention is devoted to the investigation of the effect of partial pressure of nitrogen p_N2 on mechanical properties of Ta–Si–N films. It was demonstrated that (1) the Ta–Si–N films exhibit an x-ray amorphous structure, (2) all films are electrically conductive but their electrical resistivity increases with increasing Si₃N₄ content from about 10⁻⁵ to about 10² Ω cm, and (3) the hardness H of the Ta–Si–N films is comparable to that of TaN films and achieves relatively high values (H≈30 GPa) and so it is considerably higher than that of a bulk Si₃N₄ material with H_Si3N4=17.2 GPa. The interrelationships between mechanical properties—hardness H, Young’s modulus E, and elastic recovery W_e—are discussed in detail. Special attention is devoted to the macrostress σ generated in the Ta–Si–N films during their growth and to the thermal stability of these films. © 2004 American Vacuum Society.

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62.20.D-	Elasticity
73.61.-r	Electrical properties of specific thin films
62.20.Qp	Friction, tribology, and hardness
68.60.Bs	Mechanical and acoustical properties
81.40.Jj	Elasticity and anelasticity, stress-strain relations
68.35.Gy	Mechanical properties; surface strains
81.40.Np	Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.43.Er	Other amorphous solids
81.15.Cd	Deposition by sputtering

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Electron backscattered diffraction study of poly-Si by Ni-mediated crystallization of amorphous silicon using a SiO₂ nanocap

Y. J. Chang, J. H. Oh, K. H. Kim, Jin Jang, D. I. Kim, and K. H. Oh

J. Vac. Sci. Technol. A 22, 650 (2004); http://dx.doi.org/10.1116/1.1714886 (5 pages) | Cited 5 times

Online Publication Date: 27 April 2004

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Low-temperature polycrystalline silicon (poly-Si) is of increasing interest for the display on glass. Among several techniques for the low-temperature poly-Si the Ni-mediated crystallization of amorphous silicon (a-Si) is promising one. We studied the crystalline orientation of the disk-shaped grains in the poly-Si formed by Ni-mediated crystallization of a-Si using a SiO₂ nanocap by electron backscattered diffraction measurements. A SiO₂ nanocap layer was formed by O₂ plasma treatment on a-Si and an ultrathin Ni layer was deposited on the nanocap. It was heated in a UV scan system for crystallization. The Ni atoms in a-Si diffused through the nanocap and formed NiSi₂ crystallites. Disk-shaped grains were then grown from these nuclei. The size of disk-shaped grains in poly-Si increases from ∼6 to ∼20 μm when the thickness of nanocap on a-Si changes from 2.4 to 3.2 nm. On the other hand, without the nanocap layer, its size is ∼3.5 μm. The crystalline quality of poly-Si is improved by introducing a nanocap layer, which is due mainly to the increase of the grain size. © 2004 American Vacuum Society.

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79.20.Kz	Other electron-impact emission phenomena
61.50.-f	Structure of bulk crystals
68.55.-a	Thin film structure and morphology
64.70.K-	Solid-solid transitions

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Metal–insulator–metal capacitors using Y₂O₃ dielectric grown by pulsed-injection plasma enhanced metalorganic chemical vapor deposition

C. Durand, C. Vallée, V. Loup, O. Salicio, C. Dubourdieu, S. Blonkowski, M. Bonvalot, P. Holliger, and O. Joubert

J. Vac. Sci. Technol. A 22, 655 (2004); http://dx.doi.org/10.1116/1.1722633 (6 pages) | Cited 13 times

Online Publication Date: 27 April 2004

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Yttrium oxide-based metal–insulator–metal (MIM) capacitors were investigated. The dielectric films were grown on Si/TiSi₂/TiN substrates using a low thermal budget metalorganic chemical vapor deposition process (T⩽350 °C). Low-temperature (450 °C) or high-temperature (700 °C) postdeposition annealings were carried out in different atmospheres (O₂ or argon). X-ray diffraction, x-ray photoelectron spectroscopy, and secondary ion mass spectrometry were used to determine the structural and microstructural changes in the films. The films were incorporated into simple MIM test structures. A significant capacitance value of the order of 2.2 fF/μm², a low leakage current density (∼10⁻⁸ A cm⁻² at ±10 V) and a high electrical breakdown field of 7–8 MV/cm were measured for capacitors prepared from as-deposited or low temperature (450 °C) annealed films. These results indicate that yttrium oxide is a very promising dielectric to be used in silicon integrated circuits applications. © 2004 American Vacuum Society.

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77.55.-g	Dielectric thin films
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk	Vapor phase epitaxy; growth from vapor phase
79.60.Bm	Clean metal, semiconductor, and insulator surfaces
79.20.Rf	Atomic, molecular, and ion beam impact and interactions with surfaces
64.70.K-	Solid-solid transitions
84.32.Tt	Capacitors

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Angular dependence of etch rates in the etching of poly-Si and fluorocarbon polymer using SF₆, C₄F₈, and O₂ plasmas

Jae-Ho Min, Gyeo-Re Lee, Jin-Kwan Lee, Sang Heup Moon, and Chang-Koo Kim

J. Vac. Sci. Technol. A 22, 661 (2004); http://dx.doi.org/10.1116/1.1722680 (9 pages) | Cited 8 times

Online Publication Date: 27 April 2004

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The dependences of etch rates on the angle of ions incident on the substrate surface in four plasma/substrate systems that constitute the advanced Bosch process were investigated using a Faraday cage designed for the accurate control of the ion-incident angle. The four systems, established by combining discharge gases and substrates, were a SF₆/poly-Si, a SF₆/fluorocarbon polymer, an O₂/fluorocarbon polymer, and a C₄F₈/Si. In the case of SF₆/poly-Si, the normalized etch rates (NERs), defined as the etch rates normalized by the rate on the horizontal surface, were higher at all angles than values predicted from the cosine of the ion-incident angle. This characteristic curve shape was independent of changes in process variables including the source power and bias voltage. Contrary to the earlier case, the NERs for the O₂/polymer decreased and eventually reached much lower values than the cosine values at angles between 30° and 70° when the source power was increased and the bias voltage was decreased. On the other hand, the NERs for the SF₆/polymer showed a weak dependence on the process variables. In the case of C₄F₈/Si, which is used in the Bosch process for depositing a fluorocarbon layer on the substrate surface, the deposition rate varied with the ion incident angle, showing an S-shaped curve. These characteristic deposition rate curves, which were highly dependent on the process conditions, could be divided into four distinct regions: a Si sputtering region, an ion-suppressed polymer deposition region, an ion-enhanced polymer deposition region, and an ion-free polymer deposition region. Based on the earlier characteristic angular dependences of the etch (or deposition) rates in the individual systems, ideal process conditions for obtaining an anisotropic etch profile in the advanced Bosch process are proposed. © 2004 American Vacuum Society.

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81.65.Cf	Surface cleaning, etching, patterning
52.77.Bn	Etching and cleaning
52.80.Hc	Glow; corona
81.05.Lg	Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.05.Cy	Elemental semiconductors

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Femtosecond pulsed laser deposition of amorphous, ultrahard boride thin films

Michael Stock and Pal Molian

J. Vac. Sci. Technol. A 22, 670 (2004); http://dx.doi.org/10.1116/1.1722714 (6 pages) | Cited 5 times

Online Publication Date: 27 April 2004

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Amorphous thin films (300–500 nm) of ultrahard AlMgB₁₀ with oxygen and carbon impurities were grown on Si (100) substrates at 300 K using a solid target of AlMgB₁₄ containing a spinel phase (MgAl₂O₄) and using a 120 fs pulsed, 800 nm wavelength Ti:sapphire laser. The films were subsequently annealed in argon gas up to 1373 K for 2 h. Scanning electron microscopy (SEM) was used to examine the particulate formation, atomic force microscopy was employed to characterize the film surface topography, x-ray diffraction and transmission electron microscopy were used to determine the microstructure, x-ray photoelectron spectroscopy was performed to examine the film composition, and nanoindentation was employed to study the hardness of thin films. The as-deposited and postannealed films (up to 1273 K) had a stochiometry of AlMgB₁₀ with a significant amount of oxygen and carbon impurities and exhibited amorphous structures for a maximum hardness of 40±3 GPa. However, postannealing at higher temperatures led to crystallization and transformation of the film to SiB₆ with a substantial loss in hardness. Results are also compared with our previous study on 23 ns, 248 nm wavelength (KrF excimer) pulsed laser deposition of AlMgB₁₄ reported in this journal [Y. Tian, A. Constant, C. C. H. Lo, J. W. Anderegg, A. M. Russell, J. E. Snyder, and P. A. Molian, J. Vac. Sci. Technol. A 21, 1055 (2003)]. © 2004 American Vacuum Society.

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68.55.A-	Nucleation and growth
81.15.Fg	Pulsed laser ablation deposition
68.35.Gy	Mechanical properties; surface strains
61.43.Er	Other amorphous solids
68.55.Ln	Defects and impurities: doping, implantation, distribution, concentration, etc.
81.40.Np	Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp	Friction, tribology, and hardness
68.55.-a	Thin film structure and morphology
68.55.Nq	Composition and phase identification
68.60.Bs	Mechanical and acoustical properties
61.66.Bi	Elemental solids
61.66.Dk	Alloys
68.37.Hk	Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp	Transmission electron microscopy (TEM)

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Effects of the insertion of a thick sp² buffer layer on the adhesion of cBN-rich film

S. F. Wong, C. W. Ong, G. K. H. Pang, K. Z. Baba-Kishi, and W. M. Lau

J. Vac. Sci. Technol. A 22, 676 (2004); http://dx.doi.org/10.1116/1.1723192 (7 pages) | Cited 5 times

Online Publication Date: 27 April 2004

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A method was proposed and examined to deposit thick cubic boron nitride (cBN)-rich layer of good adhesion to silicon substrate. The method combined (i) the insertion of a thick sp² buffer layer, and (ii) the use of an appropriate assist ion beam energy for the growth of the cBN-rich top layer. The sp²-bonded boron nitride buffer layer was deposited under irradiation of ions with energies in the range of 200–360 eV. The buffer layer was found to contain curled graphitic basal planes, and so was supposed to be relatively deformable, and facilitate the relaxation of stresses in the cBN-rich top layer. The ion assist introduced during the growth of the cBN-rich layer was supposed to both create and annihilate defects, and so resulted in the generation and relaxation of internal stresses. Results showed that the insertion of a 492 nm sp² buffer layer, and the use of a beam energy of 450 eV for assisting the growth of the top layer can produce a 643-nm-thick cBN-rich top layer with satisfactory adhesion, a high cBN content of 87 vol %, a hardness of 57 GPa, and an elastic modulus of 612 GPa. © 2004 American Vacuum Society.

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68.35.Np	Adhesion
82.30.Nr	Association, addition, insertion, cluster formation
68.35.Gy	Mechanical properties; surface strains
68.60.Bs	Mechanical and acoustical properties
81.15.Jj	Ion and electron beam-assisted deposition; ion plating
62.20.D-	Elasticity
62.20.Qp	Friction, tribology, and hardness
81.40.Np	Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Jj	Elasticity and anelasticity, stress-strain relations

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Thioethanol on Cu(111) at room temperature: A near edge x-ray absorption fine structure and x-ray photoelectron spectroscopy study

J. A. Syed, S. A. Sardar, S. Yagi, and K. Tanaka

J. Vac. Sci. Technol. A 22, 683 (2004); http://dx.doi.org/10.1116/1.1724837 (6 pages) | Cited 2 times

Online Publication Date: 27 April 2004

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Orientation and charge transfer upon adsorption of thioethanol on copper surface at room temperature has been studied by near edge x-ray absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS) techniques. It is found that thioethanol adsorbs dissociatively on the Cu(111) surface. Polarization dependent S K-edge NEXAFS indicates that the S–C bond is tilted 47±7° from the surface. Above 400 K, the S–C bond breaks and creates atomic sulfur. An amount of charge transfer (one electron) from copper to thioethanol molecules was measured using S 1s XPS. © 2004 American Vacuum Society.

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78.70.Dm	X-ray absorption spectra
79.60.Dp	Adsorbed layers and thin films
68.43.Mn	Adsorption kinetics
82.30.Fi	Ion-molecule, ion-ion, and charge-transfer reactions
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces

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Investigation and modeling of plasma-wall interactions in inductively coupled fluorocarbon plasmas

E. A. Joseph, B. Zhou, S. P. Sant, L. J. Overzet, and M. J. Goeckner

J. Vac. Sci. Technol. A 22, 689 (2004); http://dx.doi.org/10.1116/1.1722614 (9 pages) | Cited 10 times

Online Publication Date: 4 May 2004

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Plasma-wall interactions in fluorocarbon based feedgas chemistries, namely CF₄, are examined in a standard inductively coupled Gaseous Electronics Conference reference cell using in situ Fourier-transform infrared spectroscopy and microwave interferometry. Measurements show the dissociation of the CF₄ feedgas into radical CF_x species, as has been observed elsewhere [M. J. Goeckner and R. A. Breun, J. Vac. Sci. Technol. A 11, 3 (1993)], and qualitatively reveal a decrease in plasma-wall interactions as wall temperature is increased. Experimental results such as plasma density, 10¹¹ cm⁻³, and CF₄ density 10¹³ cm⁻³, are further compared to results from the hybrid plasma equipment model [R. Kinder and M. J. Kushner, J. Vac. Sci. Technol. A 19, 76 (2001)] to better elucidate the influence of wall temperature on plasma exposed surfaces and sticking coefficients. Last, CF₄ vibrational temperatures were also measured, revealing that the line-averaged vibrational temperature remains at a constant 40–60 K above the chamber wall temperature while the vibrational temperature in the center of the discharge is significantly higher. Moreover, the vibrational temperatures are further compared to results from a global thermal model and are in good agreement. © 2004 American Vacuum Society.

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52.40.Hf	Plasma-material interactions; boundary layer effects
52.70.Kz	Optical (ultraviolet, visible, infrared) measurements
52.65.-y	Plasma simulation
52.80.-s	Electric discharges

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Phase transition behavior of reactive sputtering deposited Co–N thin films using transmission electron microscopy

Jau-Shiung Fang, Li-Chung Yang, Chen-Siang Hsu, Gin-Shiang Chen, Yen-Wei Lin, and Giin-Shan Chen

J. Vac. Sci. Technol. A 22, 698 (2004); http://dx.doi.org/10.1116/1.1722656 (7 pages) | Cited 11 times

Online Publication Date: 4 May 2004

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Cobalt nitride thin films could be prepared by employing a direct current reactive sputtering deposition on (100) silicon substrates in mixtures of fixed Ar (4×10⁻¹ Pa) and N₂ at various partial pressures. The Co_xN thin films could be tailored by appropriately controlling the partial pressure of the reactive nitrogen. With adequately increasing nitrogen to argon partial pressure, a series of sequence phase formation from α-Co, Co₄N, Co₃N, Co₂N, and CoN could be observed. The phase transition sequence was accompanied by a substantial refinement and improvement of the films’ grain structure. Rapid thermal annealing of cobalt nitride thin films exhibited a stepwise decomposition via the dissociating of Co₄N→Co₃N+β-Co(N), Co₃N→Co₂N+β-Co(N), and Co₂N→CoN+β-Co(N) with increasing the elevated temperature. Phase formation, thermal decomposition, electrical resistivity, and microstructure of reactive sputtered cobalt nitride films were discussed in this study. © 2004 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
73.61.At	Metal and metallic alloys
64.70.Nd	Structural transitions in nanoscale materials
61.46.-w	Structure of nanoscale materials
81.15.Cd	Deposition by sputtering
81.40.Gh	Other heat and thermomechanical treatments
75.50.Tt	Fine-particle systems; nanocrystalline materials
81.07.Bc	Nanocrystalline materials
68.55.A-	Nucleation and growth
82.30.Lp	Decomposition reactions (pyrolysis, dissociation, and fragmentation)

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Outgassing properties of the spallation neutron source ring vacuum chambers coated with titanium nitride

P. He, H. C. Hseuh, M. Mapes, R. Todd, D. Weiss, and D. Wilson

J. Vac. Sci. Technol. A 22, 705 (2004); http://dx.doi.org/10.1116/1.1722697 (6 pages) | Cited 2 times

Online Publication Date: 4 May 2004

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The stainless steel vacuum chambers of the 248 m accumulator ring of the Spallation Neutron Source are to be coated with ∼100 nm of titanium nitride (TiN). This is to minimize the secondary electron yield from the chamber wall, and thus avoid the so-called e–p instability caused by electron multipacting as observed in a few high-intensity proton storage rings. Reports in the literature suggest that a TiN coating, by acting as a hydrogen permeation barrier, may also reduce the ultimate outgassing rate. The outgassing rate of TiN coated chambers deposited at various sputtering pressures was measured and compared to uncoated chambers, both with and without 250 °C in situ bake. Some coated chambers were subjected to glow discharge treatment (GDT). It was found that the surface roughness, analyzed with a scanning electron microscope, depends on the deposition pressure and is also influenced by GDT. The outgassing rate varies as a function of the surface roughness of the TiN layer, with rougher coatings more hydroscopic in nature. The in situ postbake outgassing rate was reduced ∼30% for a chamber coated with TiN at low pressure and subsequently subjected to GDT, thus giving evidence that the TiN layer acts as a permeation barrier to hydrogen diffusion. It was also found that a 450 °C vacuum degas reduced the hydrogen outgassing rate one order of magnitude, although the amount of reduction does not agree with the value predicted by standard diffusion equations. © 2004 American Vacuum Society.

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07.30.Bx	Degasification, residual gas
29.25.Dz	Neutron sources

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Spectroscopic ellipsometry characterization of ZrO₂ films on Si(100) deposited by high-vacuum-metalorganic chemical vapor deposition

Z. Song, B. R. Rogers, and N. D. Theodore

J. Vac. Sci. Technol. A 22, 711 (2004); http://dx.doi.org/10.1116/1.1690252 (8 pages) | Cited 16 times

Online Publication Date: 6 May 2004

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The integration of high-k dielectric materials into semiconductor devices requires nondestructive, fast, and accurate characterization methods. Spectroscopic ellipsometry (SE) is an outstanding candidate for this purpose. A multisample variable-angle SE method was used to characterize ZrO₂ samples deposited on Si(100) by high-vacuum chemical vapor deposition. Proper modeling of the optical properties of the interfacial layer is found to be the key to accurate characterization of ZrO₂ films. Based on a stacking model consisting of an effective medium approximation surface-roughness layer, a Tauc–Lorentz (TL) layer to represent the ZrO₂ layer, and a second TL layer to represent the interfacial layer, we accurately extract both thickness and optical constants of each layer. The extracted surface-roughness and thickness values were confirmed by atomic force microscopy and transmission electron microscopy results. The optical constants of the interfacial layer suggest that the interfacial layer is composed of nonstoichiometric zirconium silicate. © 2004 American Vacuum Society.

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78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk	Vapor phase epitaxy; growth from vapor phase
77.55.-g	Dielectric thin films

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Phase and structural characterization of vanadium oxide films grown on amorphous SiO₂/Si substrates

Doo-Hyeb Youn, Hyun-Tak Kim, Byung-Gue Chae, Young-Joo Hwang, Ju-Wook Lee, Sung-Lyul Maeng, and Kwang-Yong Kang

J. Vac. Sci. Technol. A 22, 719 (2004); http://dx.doi.org/10.1116/1.1723217 (6 pages) | Cited 13 times

Online Publication Date: 4 May 2004

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The VO₂ multiphases such as V₂O₅, VO₂, and V₂O₃ are confirmed and the correlations between structural characteristics and growth conditions was investigated using the scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). Also, the electrical characteristics of VO₂-based three terminal devices, attributed to structural and phase changes, are discussed. The spectra of VO₂ have three peaks composed of VO₂ at binding energy (BE)=516.2 eV, V₂O₃ at BE=515.6 eV, and V₂O₅ at BE=517.0 eV. With increase in the growth temperature, crystal quality of VO₂ films improves and approaches single phase of VO₂, then the peak position shifts to the spectra of oxygen-poor phase (V₂O₃). With increase in the O₂ flow, the peak position shifts to the spectra of oxygen-rich phase (V₂O₅). VO₂ films grown at optimal growth conditions have a change in resistivity of the order of 10² near a critical temperature, T_c=340 K. © 2004 American Vacuum Society.

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68.55.-a	Thin film structure and morphology
68.55.Nq	Composition and phase identification
73.61.Ng	Insulators
73.50.Dn	Low-field transport and mobility; piezoresistance
64.70.K-	Solid-solid transitions
79.60.-i	Photoemission and photoelectron spectra

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Optical characteristics and color of TiN/SiN_1.3 nanocomposite coatings

P. Jedrzejowski, B. Baloukas, J. E. Klemberg-Sapieha, and L. Martinu

J. Vac. Sci. Technol. A 22, 725 (2004); http://dx.doi.org/10.1116/1.1723252 (9 pages) | Cited 10 times

Online Publication Date: 6 May 2004

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Decorative and protective coatings deposited by dry methods are very attractive due to the environmental restrictions on traditional wet chemical techniques. In this context, nanocomposite hard coatings were fabricated by plasma enhanced chemical vapor deposition from TiCl₄/SiH₄/N₂/H₂/Ar gas mixtures at substrate temperatures of 300 and 500 °C. Their optical characteristics such as refractive index, extinction coefficient, luminosity, and colors were quantitatively determined by spectroscopic ellipsometry and spectrophotometry. Pure TiN exhibited a metal-like behavior, and its optical properties were modeled by the Drude (free carrier) approach. Nanocomposite films consisting of about 5–10 nm size TiN grains incorporated in an amorphous SiN_1.3 matrix were modeled by a sum of Drude and Lorentz (interband) transitions. Optical properties of the films were explained by their morphology and chemical structure, investigated by a multitechnique approach using scanning electron microscopy, transmission electron microscopy, elastic recoil detection in the time-of-flight regime, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy. Subsequent addition of Si to TiN caused a complex transformation from a polycrystalline to nanocomposite microstructure, which adopted a predominantly amorphous character. This was accompanied by a transition from a metallic to a dielectric behavior in terms of the optical response and electronic properties. © 2004 American Vacuum Society.

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78.66.Bz	Metals and metallic alloys
61.46.-w	Structure of nanoscale materials
42.79.Wc	Optical coatings
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.40.Gh	Other heat and thermomechanical treatments
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.37.Xy	Scanning Auger microscopy, photoelectron microscopy
79.20.Fv	Electron impact: Auger emission
79.60.Jv	Interfaces; heterostructures; nanostructures
78.30.Er	Solid metals and alloys
68.37.Hk	Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp	Transmission electron microscopy (TEM)
68.47.De	Metallic surfaces
68.55.Ln	Defects and impurities: doping, implantation, distribution, concentration, etc.

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High vacuum end cap design for use with quartz tubes

David W. Weyburne and Qing S. Paduano

J. Vac. Sci. Technol. A 22, 734 (2004); http://dx.doi.org/10.1116/1.1697486 (1 page)

Online Publication Date: 6 May 2004

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Abstract Unavailable

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07.30.Kf	Vacuum chambers, auxiliary apparatus, and materials
07.30.Hd	Vacuum testing methods; leak detectors

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Construction of a variable aperture cell for source flux control in a molecular-beam epitaxy environment

Terry J. Mattord, Michael M. Oye, David Gotthold, Chad Hansing, Archie L. Holmes, and Ben G. Streetman

J. Vac. Sci. Technol. A 22, 735 (2004); http://dx.doi.org/10.1116/1.1710495 (4 pages) | Cited 3 times

Online Publication Date: 6 May 2004

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A molecular-beam source utilizing instant flux adjustment for growth rate control is presented. The design uses a two-filament pyrolytic boron nitride (pBN) heater constructed with eight heated exit aperture holes, masked by an aperture-mating pBN closed end cylinder. The rotatable pBN mask opens and closes the effusion cell apertures to provide mechanical control of the source flux. This adjustment is provided by a rotational manipulator that translates rotary motion through the vacuum environment to the mounting journal of the pBN mask cylinder. RHEED oscillation changes in GaAs homoepitaxial growth shows an effectively instantaneous change of nearly an order of magnitude in the growth rate. © 2004 American Vacuum Society.

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81.15.Hi	Molecular, atomic, ion, and chemical beam epitaxy
85.40.Sz	Deposition technology
61.05.jh	Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.55.A-	Nucleation and growth

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Erratum: Extremely low-outgassing material: 0.2% beryllium copper alloy [J. Vac. Sci. Technol. A 22, 181 (2004)]

Fumio Watanabe

J. Vac. Sci. Technol. A 22, 739 (2004); http://dx.doi.org/10.1116/1.1735958 (1 page) | Cited 3 times

Online Publication Date: 6 May 2004

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Abstract Unavailable

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99.10.Cd	Errata
07.30.Bx	Degasification, residual gas
81.05.Bx	Metals, semimetals, and alloys

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Nano patterning on optical fiber and laser diode facet with dry resist

P. S. Kelkar, J. Beauvais, E. Lavallée, D. Drouin, M. Cloutier, D. Turcotte, Pan Yang, Lau Kien Mun, R. Legario, Y. Awad, and V. Aimez

J. Vac. Sci. Technol. A 22, 743 (2004); http://dx.doi.org/10.1116/1.1667503 (4 pages) | Cited 4 times

Online Publication Date: 11 May 2004

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Semiconductor micro and nanofabrication lithography techniques for application in microelectronics as well as in micromechanics and optoelectronics can gain significantly from using a dry resist process, since it enables the deposition of a very uniform lithographically sensitive layer on a potentially very small area. This would otherwise be extremely difficult to achieve by using a traditional spin coated resist, such as poly(methylmethacrylate) (PMMA). We demonstrate the use of an electron sensitive sterol based evaporated electron beam resist to fabricate high-resolution features (down to 100 nm) on a small surface area. This electron beam resist has a sensitivity comparable to PMMA and is deposited using a simple thermal evaporation. Two practical applications are explored: first, this resist makes it possible to fabricate a Fresnel zone plate lens on the tip of an optical fiber in order to demonstrate the principle and the potential of highly efficient coupling of diode laser emission into the fiber; second, we use this evaporated electron beam resist in order to pattern an optical diffractive element on the facet of a semiconductor laser. © 2004 American Vacuum Society.

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81.16.Nd	Micro- and nanolithography
85.40.Hp	Lithography, masks and pattern transfer
85.85.+j	Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.60.-q	Optoelectronic devices
42.82.Cr	Fabrication techniques; lithography, pattern transfer
42.81.Qb	Fiber waveguides, couplers, and arrays
42.55.Px	Semiconductor lasers; laser diodes
42.79.Ci	Filters, zone plates, and polarizers
42.79.Bh	Lenses, prisms and mirrors

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Cold wall chemical vapor deposition of single walled carbon nanotubes

P. Finnie, J. Bardwell, I. Tsandev, M. Tomlinson, M. Beaulieu, J. Fraser, and J. Lefebvre

J. Vac. Sci. Technol. A 22, 747 (2004); http://dx.doi.org/10.1116/1.1689301 (5 pages) | Cited 5 times

Online Publication Date: 11 May 2004

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Single walled carbon nanotubes (SWNTs) are emerging as a material system for electronics and optoelectronics. Hot wall thermal chemical vapor deposition (CVD) has become a standard method of preparing SWNTs. We have been using a closely related synthesis process, cold wall CVD, to produce SWNTs. Grown materials are characterized by scanning electron microscopy and photoluminescence (PL) spectroscopy. Nanotubes exceeding 150 μm in length are observed, with growth rates of at least 0.5 μm/s. PL was used to confirm the growth of SWNTs, and underscores the suitability of the material for optical and optoelectronic applications. Advantages and disadvantages of the cold wall CVD method will be described. This work shows that the cold wall CVD technique specifically is capable of producing SWNTs, and also demonstrates the use of PL as a characterization tool. © 2004 American Vacuum Society.

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81.07.De	Nanotubes
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Hx	Other solid inorganic materials

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Numerical simulations of variable range hopping conductivity in deoxyguanosine deoxyribose nucleic acid nucleoside films

Mahi R. Singh and Chi-Ming Tsang

J. Vac. Sci. Technol. A 22, 752 (2004); http://dx.doi.org/10.1116/1.1688360 (3 pages)

Online Publication Date: 11 May 2004

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Numerical simulations are performed for conductivity due to the variable range hopping conduction in deoxyribose nucleic acid nucleotides (deoxyguanosine). Self-assembled deoxyguanosine (SAD) crystals are composed of H-bonded planar ribbons, which tend to stack and form solid-state fibers. These ribbons are connected to each other by a π–π bond and form crystalline and amorphous films. We consider that the carriers are localized in H bond and π–π bond sites and the hopping conduction is the result of many series of hops in these sites. The electric field and temperature dependent conductivity expressions are used to explain the conductivity experiments of SAD films. Good agreement between theory and experiment is found. © 2004 American Vacuum Society.

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87.14.G-	Nucleic acids
87.15.A-	Theory, modeling, and computer simulation
73.50.Dn	Low-field transport and mobility; piezoresistance
82.39.Jn	Charge (electron, proton) transfer in biological systems

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Variable current transport in polymer thin film transistors

Ognian Marinov, M. Jamal Deen, Jianfei Yu, George Vamvounis, Steven Holdcroft, and William Woods

J. Vac. Sci. Technol. A 22, 755 (2004); http://dx.doi.org/10.1116/1.1649988 (5 pages) | Cited 4 times

Online Publication Date: 11 May 2004

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The performance of polymer thin film transistors, made of different semiconducting polymers, depends mostly on the type of polymer and its deposition conditions. For these polymer field-effect transistors (PFETs), the current transport is limited by the carrier injection from the source electrode into the polymer. The disordered polymer molecules near the injection interface randomize and decrease the injection barrier, resulting in a large variation of the PFET characteristics, such as threshold voltage, leakage current, and mobility. The PFET current–voltage characteristics degrade at temperatures higher than 40 °C and the low frequency noise increases by 0.3 dB/°C. © 2004 American Vacuum Society.

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73.50.Dn	Low-field transport and mobility; piezoresistance
85.30.Tv	Field effect devices
61.41.+e	Polymers, elastomers, and plastics
73.61.Ph	Polymers; organic compounds

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Oligo-p-phenylevinylene organic thin-film transistors with chemically modified dielectric surfaces

T. C. Gorjanc, I. Lévesque, and M. D’iorio

J. Vac. Sci. Technol. A 22, 760 (2004); http://dx.doi.org/10.1116/1.1647590 (4 pages) | Cited 4 times

Online Publication Date: 11 May 2004

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In this article, we report on organic thin film transistors based on a modified oligo-p-phenylevinylene oligomer, 1,4-bis[4-(4-octylphenyl)styryl]-benzene (oligo-S) on chemically modified gate dielectrics. Previously, we have reported on oligo-S devices fabricated on unmodified SiO₂ surfaces [T. C. Gorjanc, I. Lévesque, C. Py, and M. D’Iorio, Appl. Phys. Lett. (submitted)]. By using either hexamethyldisilazane (HMDS) or octadecyltrichlorosilane (OTS), both the hole mobility and on/off current ratios, I_on/off, have been increased. Maximum mobilities and on/off ratios of 0.14 cm²/V s with I_on/off>10⁶ and 0.26 cm²/V s with I_on/off>10⁷ were achieved with HMDS and OTS modified devices, respectively. © 2004 American Vacuum Society.

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85.30.Tv	Field effect devices
73.61.Ph	Polymers; organic compounds
72.20.Fr	Low-field transport and mobility; piezoresistance

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Microcavity organic light emitting diodes with double sided light emission of different colors

X. Liu, D. Poitras, Y. Tao, and C. Py

J. Vac. Sci. Technol. A 22, 764 (2004); http://dx.doi.org/10.1116/1.1722327 (4 pages) | Cited 2 times

Online Publication Date: 11 May 2004

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An organic light emitting diode was fabricated using a thin semitransparent Mg:Ag metal film (30 nm) and a distributed Bragg reflector with a reflectance of 99.5% as a microcavity. Double-sided electroluminescence was observed: green from the metal side and red from the glass side, both in directions normal to the surface. A maximum luminance of 2523 cd/m² was obtained from the metal side, where most light was coupled out of the cavity. © 2004 American Vacuum Society.

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85.60.Jb	Light-emitting devices
78.60.Fi	Electroluminescence

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Fabrication of short channel organic thin film transistors by Si-etching method

Y. Chen, W. W. Zhu, S. Xiao, and I. Shih

J. Vac. Sci. Technol. A 22, 768 (2004); http://dx.doi.org/10.1116/1.1722455 (3 pages) | Cited 5 times

Online Publication Date: 11 May 2004

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By using a Si etching and oxidation method, drain and source patterns for organic thin film transistors (OTFTs) have been fabricated without the need of precise mask alignment. OTFTs were fabricated on these patterns by spin coating a layer of Poly [2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]. From measurement results on devices with different channel lengths down to 0.5 μm, a pronounced short channel effect was observed. © 2004 American Vacuum Society.

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85.30.Tv	Field effect devices
81.65.Mq	Oxidation
81.65.Cf	Surface cleaning, etching, patterning
85.40.Hp	Lithography, masks and pattern transfer

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Organometallic vapor phase epitaxy of GaAs_1−xN_x alloy layers on GaAs(001): Nitrogen incorporation and lattice parameter variation

J.-N. Beaudry, R. A. Masut, P. Desjardins, P. Wei, M. Chicoine, G. Bentoumi, R. Leonelli, F. Schiettekatte, and S. Guillon

J. Vac. Sci. Technol. A 22, 771 (2004); http://dx.doi.org/10.1116/1.1689296 (5 pages) | Cited 8 times

Online Publication Date: 11 May 2004

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Epitaxial GaAs_1−xN_x alloy layers, nominally 200-nm-thick, with x up to 0.0375 were grown on GaAs(001) at temperatures T_s varying from 500 to 650 °C to investigate nitrogen incorporation and lattice parameter variations during organometallic vapor phase epitaxy from trimethylgallium, tertiarybutylarsine, and 1,1-dimethylhydrazine. Quantitative secondary ion mass spectrometry measurements (SIMS) indicate that N incorporation decreases systematically with increasing T_s to become almost negligible at 650 °C. All films are coherent with the substrate as judged by high-resolution x-ray reciprocal lattice mapping although atomic force microscopy and cross-sectional transmission electron microscopy reveal the presence of cracks in films with x>0.02. High-resolution x-ray diffraction measurements combined with SIMS analyses indicate that the lattice constant decreases linearly with increasing x following closely the predictions of Vegard’s rule for x<0.03. At higher concentrations, the lattice constant decreases more rapidly as a significant fraction of N atoms becomes incorporated in nonsubstitutional sites as demonstrated by nuclear reaction analysis. © 2004 American Vacuum Society.

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81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk	Vapor phase epitaxy; growth from vapor phase
61.66.Fn	Inorganic compounds
68.55.-a	Thin film structure and morphology
81.40.Np	Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M-	Structural failure of materials

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Empirical tight-binding calculations of the electronic structure of dilute III–V–N semiconductor alloys

S. Turcotte, N. Shtinkov, P. Desjardins, R. A. Masut, and R. Leonelli

J. Vac. Sci. Technol. A 22, 776 (2004); http://dx.doi.org/10.1116/1.1688361 (5 pages) | Cited 1 time

Online Publication Date: 11 May 2004

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We present empirical tight-binding (TB) calculations of the electronic structure of GaP_1−xN_x and In_yGa_1−yAs_1−xN_x alloys with low nitrogen content (x<0.05) over the entire Brillouin zone. Following the method recently developed for GaAs_1−xN_x [Shtinkov et al., Phys. Rev. B 67, 081202 (2003)], we add to the TB basis an additional anion s orbital (s_N) in order to account for the N-induced change of the electronic structure. The band structures of GaP_1−xN_x and In_yGa_1−yAs_1−xN_x are calculated using an sp³d⁵s^∗s_N TB parametrization. Our TB results are in excellent agreement with experimental and other theoretical data without introducing any additional fitting parameters, demonstrating that the developed method is a promising tool for modeling a wide range of dilute nitride materials and heterostructures. © 2004 American Vacuum Society.

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71.20.Nr	Semiconductor compounds
71.15.Ap	Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

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High-speed Si resonant cavity enhanced photodetectors and arrays

M. S. Ünlü, M. K. Emsley, O. I. Dosunmu, P. Muller, and Y. Leblebici

J. Vac. Sci. Technol. A 22, 781 (2004); http://dx.doi.org/10.1116/1.1647591 (7 pages) | Cited 4 times

Online Publication Date: 14 May 2004

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Over the past decade a new family of optoelectronic devices has emerged whose performance is enhanced by placing the active device structure inside a Fabry–Perot resonant microcavity [P. E. Green, IEEE Spectrum 13 (2002)]. The increased optical field allows photodetectors to be made thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. We have demonstrated a variety of resonant cavity enhanced (RCE) photodetectors in compound semiconductors [B. Yang, J. D. Schaub, S. M. Csutak, D. J. Rogers, and J. C. Campbell, IEEE Photonics Technol. Lett. 15, 745 (2003)] and Si [M. K. Emsley, O. I. Dosunmu, and M. S. Ünlü, IEEE J. Selected Topics Quantum Electron. 8, 948 (2002)], operating at optical communication wavelengths ranging from 850 nm to 1550 nm. The focus of this article is on Si photodetectors and arrays. High bandwidth short distance communications standards are being developed based on parallel optical interconnect fiber arrays to meet the needs of increasing data rates of interchip communication in modern computer architecture. To ensure that this standard becomes an attractive option for computer systems, low cost components must be implemented on both the transmitting and receiving end of the fibers. To meet this low cost requirement silicon based receiver circuits are the most viable option, however, high speed, high efficiency silicon photodetectors present a technical challenge. Commercially reproducible silicon wafers with a high reflectance buried distributed Bragg reflector (DBR) have been designed and fabricated [M. K. Emsley, O. I. Dosunmu, and M. S. Ünlü, IEEE J. Selected Topics Quantum Electron. 8, 948 (2002)]. The substrates consist of a two-period, 90% reflecting, DBR fabricated using a double silicon-on-insulator (SOI) process. Resonant-cavity-enhanced (RCE) Si photodetectors have been fabricated with 40% quantum efficiency at 850 nm and a FWHM of 29 ps suitable for 10 Gbps data communications. Recently, 1×12 photodetector arrays have been fabricated, packaged, and tested with silicon based amplifiers to demonstrate the feasibility of a low cost solution for optical interconnects. © 2004 American Vacuum Society.

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42.79.Sz	Optical communication systems, multiplexers, and demultiplexers
42.82.Ds	Interconnects, including holographic interconnects
42.79.Ta	Optical computers, logic elements, interconnects, switches; neural networks
85.60.Gz	Photodetectors (including infrared and CCD detectors)

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1.5 μm to 0.87 μm optical upconversion using wafer fusion technology

H. Luo, D. Ban, H. C. Liu, A. J. SpringThorpe, Z. R. Wasilewski, M. Buchanan, and R. Glew

J. Vac. Sci. Technol. A 22, 788 (2004); http://dx.doi.org/10.1116/1.1689300 (4 pages) | Cited 7 times

Online Publication Date: 14 May 2004

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Wafer fusion is an important processing tool for heterogenous integration of different materials regardless of their lattice constants. It removes the limitation of conventional epitaxial growth techniques and introduces a design parameter for achieving high performance semiconductor devices. In this article, we propose and demonstrate a 1.5 μm to 0.87 μm optical upconversion device based on wafer fusion technology. The device consists of an In_0.53Ga_0.47As (InGaAs) p-i-n photodetector and an AlGaAs/GaAs light-emitting diode (LED) integrated with wafer fusion. Incoming 1.5 μm light is absorbed by the InGaAs photodetector and generates a photocurrent. The resultant photocurrent drives the GaAs LED, which emits radiation at 0.87 μm. An internal quantum efficiency of 20% and an external quantum efficiency of 0.27% was obtained at room temperature. The results show the potential of the upconversion device in near-infrared imaging applications.

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85.30.Kk	Junction diodes
85.60.Jb	Light-emitting devices
42.65.Ky	Frequency conversion; harmonic generation, including higher-order harmonic generation
85.60.Bt	Optoelectronic device characterization, design, and modeling

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Growth of InGaN self-assembled quantum dots and their application to photodiodes

L. W. Ji, Y. K. Su, S. J. Chang, S. T. Tsai, S. C. Hung, R. W. Chuang, T. H. Fang, and T. Y. Tsai

J. Vac. Sci. Technol. A 22, 792 (2004); http://dx.doi.org/10.1116/1.1722353 (4 pages) | Cited 1 time

Online Publication Date: 14 May 2004

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Nanometer-scale InGaN self-assembled quantum dots (QDs) have been prepared by growth interruption during metalorganic chemical vapor deposition growth. With a 12 s growth interruption, we successfully formed InGaN QDs with a typical lateral size of 25 nm and an average height of 4.1 nm. The QD density was about 2×10¹⁰ cm⁻². In contrast, much larger InGaN QDs were obtained without growth interruption. InGaN metal-semiconductor-metal photodiodes with and without QDs were also fabricated. It was found that the QD photodiode with lower dark current could operate in the normal incidence mode, and exhibit a stronger photoresponse. © 2004 American Vacuum Society.

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SECTION LISTING

BROWSE VOLUMES

May 2004

Volume 22, Issue 3, pp. L1-1082