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Nov 2006

Volume 24, Issue 6, pp. L11-2228

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Influence of background gas pressure charging potential and target distance on the spot size ablated by single pulsed electron beam

Roberto S. Aga, Chase Cox, Akira Ueda, Enrique Jackson, W. E. Collins, and Richard Mu

J. Vac. Sci. Technol. A 24, L11 (2006); http://dx.doi.org/10.1116/1.2360970 (4 pages) | Cited 2 times

Online Publication Date: 19 October 2006

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The area of spot ablated by single pulsed electron beam has been measured as a function of pulsed electron deposition (PED) parameters. These parameters are background gas pressure, charging potential and target distance. A 50 nm thick film of silver on glass is used as ablation target in order to create a clear spot that can be measured. The spot area is found to reflect the power density of the pulsed electron beam and it can be varied by adjusting the PED parameters. These results are useful in the application of PED for material fabrication.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.80.Fe Electron and positron radiation effects
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Quadrupole mass spectrometry desorption analysis of Ga adsorbate on AlN (0001)

Jay S. Brown, Gregor Koblmüller, Robert Averbeck, Henning Riechert, and James S. Speck

J. Vac. Sci. Technol. A 24, 1979 (2006); http://dx.doi.org/10.1116/1.2338554 (6 pages) | Cited 3 times

Online Publication Date: 10 October 2006

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The authors have investigated the adsorption and subsequent desorption of Ga on AlN (0001) with line-of-sight quadrupole mass spectrometry (QMS). The authors present desorption data consistent with a continuous Ga-flux dependent accumulation of a laterally contracted Ga bilayer on AlN (0001) from 0 to 2.7±0.3 ML GaN equivalent coverage, and further Ga accumulation in macroscopic Ga droplets. The temperature dependence of Ga-adsorbate QMS desorption transients was investigated and the authors determined that the desorption activation energies for individual monolayers of the Ga adsorbate on AlN (0001) were similar to Ga desorption from GaN (0001). For the (first) pseudomorphic Ga-adsorbate monolayer on AlN, the authors measured a maximum Ga coverage of 1.0±0.1 ML and desorption activation energy of 6.2±0.3 eV. For the (second) laterally contracted Ga monolayer (1.7±0.3 ML) the desorption activation energy was 3.8±0.1 eV.
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68.43.Mn Adsorption kinetics
68.47.Fg Semiconductor surfaces

Effects of oxygen pressure on the microstructure of LaNiO3 conductive thin film monitored by in situ reflection high energy diffraction

Jun Zhu, Liang Zheng, Xian Hua Wei, Ying Zhang, and Yan Rong Li

J. Vac. Sci. Technol. A 24, 1985 (2006); http://dx.doi.org/10.1116/1.2338556 (7 pages) | Cited 2 times

Online Publication Date: 10 October 2006

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LaNiO3 (LNO) conductive thin films with different thicknesses were deposited on SrTiO3 (100) substrates in different oxygen pressures. Effects of oxygen pressure on microstructure of LNO conductive film have been studied by in situ reflection high energy electron diffraction (RHEED) and ex situ x-ray photoelectron spectroscopy (XPS). In the relatively low oxygen pressure, LNO film displays spotty RHEED pattern. When the thickness increases up to a critical value, about 30 nm, the spotty RHEED pattern gradually changes to streaky pattern, and the RHEED oscillation curve appears. The streaky RHEED pattern of LNO film deposited in the relatively high oxygen pressure can be observed at the initial growth. With pumping the oxygen pressure to a relatively low value, the RHEED pattern gradually changes to spotty one. When the oxygen pressure is increased back to a high value, the RHEED pattern changes to streaky one again. This RHEED pattern transformation induced by the oxygen pressure is reversible. Ex situ XPS results indicate that the element Ni of LNO film deposited in the relatively low oxygen pressure with a thickness below the critical value exists in the form as Ni2+ while as Ni3+ in the relatively high oxygen pressure. When the thickness increases to the critical value, the chemical valence of element Ni in the top layers of LNO film deposited in the relatively low oxygen pressure is +3. A mechanism of effects of oxygen pressure on microstructure of LaNiO3 conductive thin film is given. This sensitivity to oxygen for LNO thin film can be used in sensor devices.
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68.55.A- Nucleation and growth
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Parametric study of sputtered Sr-deficient SrBi2Ta2O9 thin films

Sam Zhang, Yibin Li, Weidong Fei, Zhenghao Gan, Subodh Mhaisalkar, and X. M. Li

J. Vac. Sci. Technol. A 24, 1992 (2006); http://dx.doi.org/10.1116/1.2338560 (7 pages)

Online Publication Date: 10 October 2006

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Sr-deficient SrBi2Ta2O9 (SBT) thin films for nonvolatile ferroelectric random access memory applications were deposited by radio-frequency magnetron sputtering on Pt/Ta/SiO2/Si substrates. The effect of deposition parameters on microstructures and chemical composition were studied using x-ray diffraction (XRD), field emission scanning electron microscopy, and x-ray photoelectron spectroscopy (XPS). The composition of the films was dependent on the sputtering conditions. The undesirable pyrochlore phase could be eliminated by adjusting process pressure, target power density, and target-to-substrate distance. The evolution of microstructures at various deposition conditions was attributed to changes in the Bi/Ta and Sr/Ta ratios. When Sr became deficient and Bi excessive (Sr0.74Bi2.2Ta2O9+x as determined by XPS), no pyrochlore phase was detected with XRD. Under an electric field of 240 kV/cm, the Sr-deficient SBT film demonstrated a remnant polarization (2Pr) of 11.6 μC/cm2 and a coercive field (2Ec) of 96 kV/cm.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
79.60.Dp Adsorbed layers and thin films

Nitriding of a tool steel with an electron-beam-excited plasma

H. Shoyama, T. Hishida, T. Hara, Y. Dake, T. Mori, H. Nagai, M. Hori, and T. Goto

J. Vac. Sci. Technol. A 24, 1999 (2006); http://dx.doi.org/10.1116/1.2338563 (4 pages) | Cited 2 times

Online Publication Date: 10 October 2006

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Nitriding of a tool steel was carried out with an electron-beam-excited plasma (EBEP). EBEP is sustained with energetic electron beams over the pressure range of 10−3–101 Pa by electron-impact ionization. Samples whose temperatures were controlled by electric radiant heater were exposed to EBEP. A nitrided layer of 100 μm and a surface hardness of 1000 HV(0.1) were achieved for tool steel SKD61 (JIS) at 800 K and a treatment time of 3 h. In order to measure the density of nitrogen atoms in EBEP, a vacuum ultraviolet absorption spectroscopy system was used. It was found that the density of nitrogen atoms increased from 1011 to 1012 cm−3 linearly with an increase of electron beam current from 2 to 20 A.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
78.40.Kc Metals, semimetals, and alloys
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
52.77.-j Plasma applications
79.20.Kz Other electron-impact emission phenomena

Writing and erasing efficiency analysis on optical-storage media using scanning surface potential microscopy

Sy-Hann Chen, Sheng-Ping Hou, J. H. Hsieh, Hsing Kuang Chen, and Din Ping Tsai

J. Vac. Sci. Technol. A 24, 2003 (2006); http://dx.doi.org/10.1116/1.2345641 (5 pages) | Cited 4 times

Online Publication Date: 10 October 2006

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The authors demonstrate a rapid and convenient method for the determination of writing and erasing laser powers in phase-change media based on scanning surface potential microscopy using a conductive tip. Commercially available digital versatile disks that are rewritable with initialization process are measured in experiments. The results of measurement show that when the disk is rotating at 3.5 m/s linear velocity, the adequate writing and erasing of laser power are 10–15 and 4–8 mW, respectively. The critical laser power for crystallization conversion is 8 mW. The method used for this research can be satisfyingly applied to the development of new phase-change recording materials.
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42.79.Vb Optical storage systems, optical disks

Integrated framework for the flux calculation of neutral species inside trenches and holes during plasma etching

George Kokkoris, Andreas G. Boudouvis, and Evangelos Gogolides

J. Vac. Sci. Technol. A 24, 2008 (2006); http://dx.doi.org/10.1116/1.2345643 (13 pages) | Cited 12 times

Online Publication Date: 10 October 2006

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An integrated framework for the neutral flux calculation inside trenches and holes during plasma etching is described, and a comparison between the two types of structure in a number of applications is presented. First, a detailed and functional set of equations for the neutral and ion flux calculations inside long trenches and holes with cylindrical symmetry is explicitly formulated. This set is based on early works [ T. S. Cale and G. B. Raupp, J. Vac. Sci. Technol. B 8, 1242 (1990) ; V. K. Singh et al., J. Vac. Sci. Technol. B 10, 1091 (1992) ], and includes new equations for the case of holes with cylindrical symmetry. Second, a method for the solution of the respective numerical task, i.e., one or a set of linear or nonlinear integral equations, is described. This method includes a coupling algorithm with a surface chemistry model and resolves the singularity problem of the integral equations. Third, the fluxes inside trenches and holes are compared. The flux from reemission is the major portion of the local flux at the bottom of both types of structure. The framework is applied in SiO2 etching by fluorocarbon plasmas to predict the increased intensity of reactive ion etching lag in SiO2 holes compared to trenches. It is also applied in deep Si etching: By calculating the flux of F atoms at the bottom of very high aspect ratio (up to 150) Si trenches and holes during the gas chopping process, the aspect ratio at which the flux of F atoms is eliminated and etching practically stops is estimated.
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81.65.Cf Surface cleaning, etching, patterning
68.47.Fg Semiconductor surfaces
52.77.Bn Etching and cleaning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Effects of low-temperature-grown buffers on pulsed-laser deposition of GaN on LiNbO3

Y. Tsuchiya, M. Oshima, A. Kobayashi, J. Ohta, and H. Fujioka

J. Vac. Sci. Technol. A 24, 2021 (2006); http://dx.doi.org/10.1116/1.2345644 (4 pages)

Online Publication Date: 10 October 2006

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The authors have investigated the effects of low-temperature-grown (LTG) GaN buffer layers on the pulsed-laser deposition of GaN films on LiNbO3. LiNbO3 substrates with atomically flat surfaces have been prepared by annealing in a box constructed from blocks of single crystal LiNbO3 wafers. When the GaN growth temperature is lowered from 700 to 580 °C, the GaN/LiNbO3 interfacial layer thickness is reduced. When these LTG-GaN layers, which have a thickness of 20 nm, are employed as buffers for the subsequent high temperature growth of 200-nm-thick GaN layers, a decrease in root-mean-square surface roughness and a reduction in tilt and twist mosaicities are observed. This technique seems quite promising for achieving high quality GaN on LiNbO3 substrates, which is attractive for the fabrication of future optoelectronic integrated circuits.
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81.05.Ea III-V semiconductors
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
68.47.Fg Semiconductor surfaces

Improved volume-averaged model for steady and pulsed-power electronegative discharges

Sungjin Kim, M. A. Lieberman, A. J. Lichtenberg, and J. T. Gudmundsson

J. Vac. Sci. Technol. A 24, 2025 (2006); http://dx.doi.org/10.1116/1.2345645 (16 pages) | Cited 34 times

Online Publication Date: 10 October 2006

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An improved volume-averaged global model is developed for a cylindrical (radius R, length L) electronegative (EN) plasma that is applicable over a wide range of electron densities, electronegativities, and pressures. It is applied to steady and pulsed-power oxygen discharges. The model incorporates effective volume and surface loss factors for positive ions, negative ions, and electrons combining three electronegative discharge regimes: a two-region regime with a parabolic EN core surrounded by an electropositive edge, a one-region parabolic EN plasma, and a one-region flat-topped EN plasma, spanning the plasma parameters and gas pressures of interest for low pressure processing (below a few hundred millitorr). Pressure-dependent effective volume and surface loss factors are also used for the neutral species. A set of reaction rate coefficients, updated from previous model calculations, is developed for oxygen for the species O2, O2(math), O, O2+, O+, and O−, based on the latest published cross-section sets and measurements. The model solutions yield all of the quantities above together with such important processing quantities such as the neutral/ion flux ratio ΓO/Γi, with the discharge aspect ratio 2R/L and pulsed-power period and duty ratio (pulse on-time/pulse period) as parameters. The steady discharge results are compared to an experiment, giving good agreement. For steady discharges, increasing 2R/L from 1 to 6 leads to a factor of 0.45 reduction in ΓO/Γi. For pulsed discharges with a fixed duty ratio, ΓO/Γi is found to have a minimum with respect to pulse period. A 25% duty ratio pulse reduces ΓO/Γi by a factor of 0.75 compared to the steady-state case.
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52.80.-s Electric discharges
52.50.Dg Plasma sources
52.25.Ya Neutrals in plasmas
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.40.Hf Plasma-material interactions; boundary layer effects

Strain mediated reconstructions and indium segregation on InGaAs/GaAs(001) alloy surfaces at intermediate lattice mismatch

A. Riposan, J. Mirecki Millunchick, and Chris Pearson

J. Vac. Sci. Technol. A 24, 2041 (2006); http://dx.doi.org/10.1116/1.2345646 (8 pages) | Cited 5 times

Online Publication Date: 10 October 2006

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In vacuo scanning tunneling microscopy is used to investigate the surface reconstructions of pseudomorphic InGaAs alloys at intermediate values of compressive strain. The coverage of different reconstructions varies with film thickness, concomitant with changes in composition and strain at the surface arising from In segregation and changes in surface morphology. Thin samples exhibit mainly disordered (1×3) reconstructions along with small regions of incommensurate (1×2). With increasing thickness, the (1×3) transforms into more regular (4×3) or c(4×6), whose coverage mirrors the increase and saturation of In surface composition. Regions of α2(2×4) reconstructions are also present, and their coverage initially increases with In surface composition, but later decreases upon saturation of In at the surface. This decrease is concurrent with the onset of surface roughening, suggesting that the α2(2×4) reconstruction is strain stabilized.
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68.47.Fg Semiconductor surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

Comparison of saturation current characteristics for ultrathin silicon oxides grown on n- and p-type silicon substrates simultaneously

Tsung-Miau Wang, Chia-Hua Chang, Shu-Jau Chang, and Jenn-Gwo Hwu

J. Vac. Sci. Technol. A 24, 2049 (2006); http://dx.doi.org/10.1116/1.2345648 (5 pages)

Online Publication Date: 10 October 2006

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Rapid thermal oxidations were simultaneously performed on n- and p-type silicon substrates to investigate the saturation currents of metal-oxide-semiconductor (MOS) capacitors. For MOS capacitors on n-type Si substrates, the curves of capacitance versus gate voltage (C-V) show almost no fixed charge, no lateral nonuniformity, and little interface trap density (Dit). The mechanism of the generation of the saturation current is recombination, and was investigated by electroluminescence. Also, the saturation current decreases as the oxide becomes thicker. However, the oxidation temperature must be sufficiently high to form high-quality oxide on p-type Si substrate. Controlled by minority carrier generation, the saturation current of the MOS (p) capacitor also depends on Dit, suboxide, and bulk trap density. The saturation current increases with the thickness of the oxide. The generation mechanism of the saturation currents of MOS (p) capacitors was also investigated by observing their dependencies on temperature. The mechanisms of the generation saturation currents of MOS capacitors grown on n- and p-type Si substrates are basically different.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
81.65.Mq Oxidation
84.32.Tt Capacitors
85.30.Tv Field effect devices
73.20.At Surface states, band structure, electron density of states
78.60.Fi Electroluminescence

Mosaic nanostructure of TiO2 with rutile short-range atomic order

C. R. Aita

J. Vac. Sci. Technol. A 24, 2054 (2006); http://dx.doi.org/10.1116/1.2345649 (7 pages) | Cited 5 times

Online Publication Date: 11 October 2006

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A nanolaminate film of six 36 nm TiO2–7 nm Al2O3 bilayers is sputter deposited at room temperature and examined by high resolution transmission electron microscopy (HRTEM). Neither the TiO2 nor the Al2O3 layers have long-range crystallographic order. Previous Raman spectroscopy of the nanolaminate showed that short-range atomic order in the TiO2 component is characteristic of bulk rutile. The HRTEM images of the Al2O3 layers consist entirely of random contrast speckle characteristic of a material with no atomic ordering beyond the nearest-neighbor level. However, the predominant feature in the images of the TiO2 layers is a mosaic structure, with fewer regions of random contrast speckle. The mosaic consists of four repetitive elements: (1) domains of {110} planes terminating along ⟨100⟩ directions, (2) planar faults along ⟨100⟩ directions, (3) {110} facets in steps along the [001] direction, and (4) a herringbone structure of short strands of (110) and (−110) planes on either side of a ⟨100⟩ midrib. We show how two combined growth operations can generate this nanostructure: These operations are the preferential three-dimensional growth of a rutile nucleus with a {110} habit and the formation of growth faults with ½〈10−1〉{011} and ½〈10−1〉{121} displacement vectors. The results explicitly show that TiO2 with rutile short-range atomic order self-assembles into units beyond the nearest-neighbor level. This behavior is different from oxides that are continuous random network formers, such as SiO2 and Al3O3, in which the metal-oxygen bonds are predominantly covalent.
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68.55.-a Thin film structure and morphology
61.46.Hk Nanocrystals
81.16.Dn Self-assembly
68.37.Lp Transmission electron microscopy (TEM)
78.30.Hv Other nonmetallic inorganics
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Interface broadening due to ion mixing during thin film growth at the radio-frequency-biased electrode in a plasma-enhanced chemical vapor deposition environment

A. Amassian, M. Svec, P. Desjardins, and L. Martinu

J. Vac. Sci. Technol. A 24, 2061 (2006); http://dx.doi.org/10.1116/1.2348642 (9 pages) | Cited 2 times

Online Publication Date: 11 October 2006

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The authors show that ion bombardment in the range of tens to a few hundreds of eV, used in ion- and plasma-assisted deposition processes, can lead to thin film growth dominated by subsurface deposition due to subplantation (shallow implantation). This can cause significant interface broadening during the initial stages of film deposition as a result of ion mixing. First, by studying the modifications of a c-Si(100) target exposed to an O2 plasma at the radio-frequency (rf)-biased electrode using in situ real-time spectroscopic ellipsometry (RTSE), the authors detect implantation, damage, and oxidation to a depth of up to ∼ 10 nm. They validate these results using high resolution transmission electron microscopy and simulate the effects of ion-surface interactions at the rf-biased electrode by using Monte Carlo TRIDYN simulations. The simulation code, which was modified specifically to consider a broadband ion energy source, enabled the authors to reproduce depth and time relevant experimental results with good agreement. In situ RTSE was then used to monitor TiO2 deposition on SiO2 under similar ion bombardment conditions. The authors observed the formation of a 2- to 4-nm-thick interfacial layer, depending on the ion-to-neutral flux ratio (ϕi/ϕn), which was controlled by varying the deposition rate. TRIDYN simulations revealed that oxygen subplantation causes interfacial broadening during the growth through ballistic mixing of Ti and Si atoms at the interface; the interface width scales as ∼ (ϕi/ϕn)1/2. Intensive ion mixing at ϕi/ϕn>1 is also shown to be responsible for the ballistic displacement of the majority of surface-deposited Ti atoms into the bulk, so that the growth appears to be dominated by subsurface deposition under conditions of intense ion bombardment.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Influence of substrate properties and annealing temperature on the stress state of magnetron sputtered tungsten thin films

J. C. Oliveira and A. Cavaleiro

J. Vac. Sci. Technol. A 24, 2070 (2006); http://dx.doi.org/10.1116/1.2348643 (6 pages)

Online Publication Date: 11 October 2006

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The influence of substrate properties and annealing temperature on the stress state of tungsten thin films deposited by dc reactive magnetron sputtering was studied using 310 steel (AISI), Fecralloy® and Invar® substrates. Besides elemental tungsten, only residual amounts of contamination elements (O, C, Ar, etc.) were detected by electron probe microanalysis. Only the α-W crystalline structure, with a preferential ⟨110⟩ orientation, was detected in all the films by x-ray diffraction. The highest lattice parameters were measured for the films deposited on 310 steel substrates, while the smallest values were obtained for the films deposited on Invar® substrates. These results are closely related to the thermal expansion coefficients of the substrates. All the as-deposited films were in a compressive stress state independent of the substrate type (−3 GPa for 310 steel and Fecralloy® substrates and −2 GPa for Invar® substrates). The residual compressive stresses of the films deposited on Fecralloy® substrates strongly decrease with annealing temperatures up to ≈ −8 GPa at 1175 K. This result shows that the measured compressive stresses are not real, and they are a direct consequence of plastic deformation of the substrate. On the contrary, the compressive stresses measured in the films deposited on Invar® and 310 steel substrates are real as plastic deformation of the substrates is not observed.
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81.05.Bx Metals, semimetals, and alloys
81.40.Gh Other heat and thermomechanical treatments
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
68.60.Bs Mechanical and acoustical properties
65.40.De Thermal expansion; thermomechanical effects

Characterization of fluorine-modified organosilicate glass

Chi-Wen Liu, Ying-Lang Wang, Yungder Juang, Shiuh-Ko JangJean, and Wen-His Lee

J. Vac. Sci. Technol. A 24, 2076 (2006); http://dx.doi.org/10.1116/1.2348644 (6 pages)

Online Publication Date: 11 October 2006

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In this study, fluorine-modified organosilicate glass (F-OSG) films were deposited by using a plasma-enhanced chemical vapor deposition technique on 3MS/O2/SiF4 mixtures to change deposition temperatures. The films were characterized by using reflectometer data, Fourier transformation infrared spectroscopy, and x-ray photoelectron spectroscopy. The authors found that film deposition rates and fluorine contents in the F-OSG films decreased while the deposition temperature increased; moreover, negative apparent activation energies for film deposition were also observed, suggesting a deposition process dominated by surface adsorption/desorption reactions. In addition, the authors also investigated the effects of Si–C and Si–F bonding on the dielectric breakdown and leakage mechanism of the F-OSG films. They found that high and two-step breakdown voltage of the F-OSG films relative to that of the OSG films can be highlighted as a consequence of the structural change accompanied by the incorporation of fluorine, and hence the leakage current behavior of F-OSG in low field conduction is well explained by the Schottky emission.
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81.05.Kf Glasses (including metallic glasses)
77.55.-g Dielectric thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
78.66.Jg Amorphous semiconductors; glasses

SiO2-like film deposition by dielectric barrier discharge plasma gun at ambient temperature under an atmospheric pressure

Qiang Chen, Yuefei Zhang, Erli Han, and Yuanjing Ge

J. Vac. Sci. Technol. A 24, 2082 (2006); http://dx.doi.org/10.1116/1.2348724 (5 pages) | Cited 5 times

Online Publication Date: 11 October 2006

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A medium-frequency dielectric barrier discharge (DBD) plasma gun was used to deposit SiO2-like films at ambient temperature under atmospheric pressure. SiO2-like films were deposited on Si and stainless-steel surfaces by flowing Ar gas containing hexamethyldisiloxane (HMDSO) monomer through the gun. The authors found that the chemical structure of the deposited SiO2-like film strongly depended on the HMDSO monomer ratio in the flowing gas and on the incident power. Fourier transform infrared spectroscopy showed no hydroxyl group in the chemical structure under the low HMDSO ratio in flowing gas or high incident plasma power. Scanning electron microscopy and atomic force microscopy revealed that SiO2-like films began to grow as islands and then formed in columns having porosity. Oxygen added to the plasma-gun flow plays a lesser role in the SiO2-like deposition from a DBD plasma gun at atmospheric pressure, and the critical temperature for pure SiO2 formation is also greatly lowered.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
52.77.Dq Plasma-based ion implantation and deposition
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.80.-s Electric discharges
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
77.55.-g Dielectric thin films

Heat transfer through a rarefied gas confined between two coaxial cylinders with high radius ratio

Felix Sharipov and Guilherme Bertoldo

J. Vac. Sci. Technol. A 24, 2087 (2006); http://dx.doi.org/10.1116/1.2353847 (7 pages) | Cited 8 times

Online Publication Date: 11 October 2006

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Heat flux through a rarefied gas confined between two coaxial cylinders is calculated on the basis of the kinetic equation. The external cylinder radius is assumed to be significantly larger than the internal one. To investigate the influence of the gas-surface interaction on the heat transfer the Cercignani-Lampis scattering kernel is applied at the internal cylinder. It is shown that the surface properties of the external cylinder weakly affect the heat transfer. Comparing the numerical results with experimental data the energy accommodation coefficient is extracted.
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47.27.te Turbulent convective heat transfer
47.60.-i Flow phenomena in quasi-one-dimensional systems

Thermal stability of sputter deposited nanocrystalline W2N/amorphous Si3N4 coatings

T. Fu, Y. G. Shen, Z. F. Zhou, and K. Y. Li

J. Vac. Sci. Technol. A 24, 2094 (2006); http://dx.doi.org/10.1116/1.2353849 (6 pages)

Online Publication Date: 11 October 2006

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The thermal stability of nanocomposite W–Si–N coatings, which had been sputter deposited at increased silicon target currents, was studied by annealing at 800 or 900 °C in vacuum by using x-ray diffraction, x-ray photoelectron spectroscopy, electron probe microanalysis, scanning electron microscopy, atomic force microscopy, and microhardness testing. The crystalline W2N coatings were decomposed to W with the loss of interstitial N atoms and the presence of microcracks at their surfaces after annealing at 900 °C. The coating consisting of nanocrystalline (nc-) W2N imbedded in amorphous (a-) Si3N4 matrices and the amorphous coatings underwent partial recrystallization, the loss of interstitial N atoms, and morphological changes upon annealing. The nc-W2N/a-Si3N4 coating had the least N in grain boundaries and the lowest atomic O/N ratio, and it had no failure after annealing at 900 °C, showing high thermal stability. The hardness of the coatings was decreased, but the nc-W2N/a-Si3N4 coating maintained the highest hardness (46.6±3.7 GPa) after annealing at 900 °C.
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81.07.Bc Nanocrystalline materials
81.05.Mh Cermets, ceramic and refractory composites
81.40.Gh Other heat and thermomechanical treatments
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
62.20.M- Structural failure of materials

Measurement of Cu atom density in a magnetron sputtering plasma source using an YBaCuO target by laser-induced fluorescence imaging spectroscopy

Junsi Gao, Nayan Nafarizal, and Koichi Sasaki

J. Vac. Sci. Technol. A 24, 2100 (2006); http://dx.doi.org/10.1116/1.2353850 (5 pages) | Cited 3 times

Online Publication Date: 11 October 2006

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In this study, the authors measured the density of Cu atoms in a magnetron sputtering plasma source employing an YBaCuO target by laser-induced fluorescence imaging spectroscopy. It was observed that, when pure Ar gas was used, the Cu density varied temporally after the initiation of the discharge. The temporal variation was examined as a function of the gas pressure and the input rf power as well as the experimental sequence. When the Ar gas pressure was 300 mTorr, the Cu density decreased to 60% of the initial value after the transient period of 6 min at a rf power of 30 W, while at a rf power of 70 W, the transient period was 10 min and the Cu density at the steady state was 30% of the initial value. The transient period and the steady-state density showed hystereses, and the different transient periods and steady-state densities were observed at different experimental sequences. On the other hand, when the mixture of Ar and O2 (0.7%) was used as the discharge gas, the Cu density was stationary at a value which was approximately 40%–60% of that observed in the pure Ar discharge at the steady state. The Cu atom density had the maximum at an O2 flow rate ratio of 7.4%.
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81.15.Cd Deposition by sputtering
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges
52.25.-b Plasma properties

Interfacial characterization and residual stress analysis in diamond films on LiNbO3

K. Jagannadham, T. R. Watkins, and M. J. Lance

J. Vac. Sci. Technol. A 24, 2105 (2006); http://dx.doi.org/10.1116/1.2356479 (8 pages)

Online Publication Date: 11 October 2006

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Diamond films were deposited via microwave plasma chemical vapor deposition on lithium niobate (LN) substrates. Characterization of the interfacial regions formed between diamond films and LN substrates was carried out by several techniques. Secondary ion mass spectroscopy (SIMS) was used to determine the depth profiles of carbon, lithium, niobium, and oxygen in the LN substrate covered with diamond nuclei and in the substrate without nucleation. Results indicate that the diamond nuclei promoted growth of diamond, and in addition, a reduced depth of the lithium deficient zone formed in the LN substrate was observed. Grazing incidence x-ray diffraction and transmission electron microscopy observations corroborated the results obtained by SIMS. Residual stresses determined experimentally by an x-ray method or by the shift in the characteristic diamond peak in Raman spectroscopy were much smaller than the calculated thermal residual stresses. The results further emphasize that the interfacial phases are responsible for relieving the thermal stresses generated during cooling of the layered structure. The thickness of the interfacial region was found to be well below for attenuation of the surface acoustic waves in the gigahertz frequency surface acoustic wave devices.
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68.35.Ct Interface structure and roughness
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
61.66.Bi Elemental solids
61.66.Dk Alloys
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.37.Lp Transmission electron microscopy (TEM)

Nitriding of AISI 4140 steel by a low energy broad ion source

E. A. Ochoa, C. A. Figueroa, and F. Alvarez

J. Vac. Sci. Technol. A 24, 2113 (2006); http://dx.doi.org/10.1116/1.2356480 (4 pages) | Cited 3 times

Online Publication Date: 11 October 2006

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A comprehensive study of the thermochemical nitriding process of steel AISI 4140 by low energy ion implantation (Kaufmann cell) is reported. Different times of implantation were employed and the studied samples were characterized by x-ray diffraction, in situ photoemission electron spectroscopy, scanning electron microscopy, and hardness (nanoindentation) measurements. The linear relationship between nitrogen content and hardness was verified. The structure of the nitrided layer was characterized yielding that the compound layer is formed by coarse precipitates, around small grains, constituted principally by ε-Fe2–3N and γ-Fe4N phases and the diffusion zone is formed by fine precipitates, around big grains of the original martensitic phase, constituted principally by γ-Fe4N phase. Finally, a diffusion model for multiphase systems was applied to determine effective diffusion coefficients of nitrogen in the different phases.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
61.82.Bg Metals and alloys
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
81.30.Mh Solid-phase precipitation

Photon stimulated ion desorption from condensed thiophene photoexcited around the S 1s-edge

M. L. M. Rocco, T. Sekiguchi, and Y. Baba

J. Vac. Sci. Technol. A 24, 2117 (2006); http://dx.doi.org/10.1116/1.2357742 (5 pages) | Cited 4 times

Online Publication Date: 12 October 2006

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Photon stimulated ion desorption and Auger decay spectra were measured for condensed thiophene around the S 1s-edge. Three kinds of ions, H+, S+, and S2+, were observed as main desorbed species. Partial ion yields (PIY) have been determined for these three fragment ions as a function of the photon energy. It was found that the indirect x-ray induced electron stimulated desorption mechanism plays an important role in H+ ion desorption. For S+ ion desorption, on the other hand, a pronounced enhancement at ∼ 3 eV away from the first core-to-valence resonance was observed in the PIY curve. On the basis of the results for the Auger decay spectra, the enhancement of S+ desorption at ∼ 3 eV away from the first resonance is interpreted in terms of the effective screening of positive holes due to the existence of Rydberg electrons.
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68.43.Tj Photon stimulated desorption
79.20.La Photon- and electron-stimulated desorption
79.20.Fv Electron impact: Auger emission
68.43.Rs Electron stimulated desorption
73.20.At Surface states, band structure, electron density of states

Reactive sputter-deposition of AlN films by dense plasma focus

Mehboob Sadiq, S. Ahmad, M. Shafiq, M. Zakaullah, R. Ahmad, and A. Waheed

J. Vac. Sci. Technol. A 24, 2122 (2006); http://dx.doi.org/10.1116/1.2357743 (6 pages) | Cited 2 times

Online Publication Date: 12 October 2006

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A low energy (1.45 kJ) dense plasma focus device is used to deposit thin films of aluminum nitride (AlN) at room temperature on silicon substrates. For deposition of films, a conventional hollow copper anode is replaced with a solid aluminum anode and nitrogen is used as fill gas. The films are deposited using a multiple number of focus shots by placing the substrate in front of the anode. The deposited films are characterized using x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, and a microhardness test. The XRD analysis of the films shows that the deposited films show strong c-axis alignment. The Raman spectra of the films indicate that the deposited films are under compressive stress and crystalline quality decreases with increasing number of focus shots. The microhardness results point toward the uniform deposition of hard AlN layers on silicon substrates.
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52.59.Hq Dense plasma focus
61.05.cp X-ray diffraction
78.30.Fs III-V and II-VI semiconductors
52.77.Dq Plasma-based ion implantation and deposition
62.20.Qp Friction, tribology, and hardness

Development of a low pressure microwave excited plasma and its application to the formation of microcrystalline silicon films

Daisuke Kikukawa, Masaru Hori, Koichiro Honma, Masahiro Yamamoto, Toshio Goto, Shunji Takahashi, and Shoji Den

J. Vac. Sci. Technol. A 24, 2128 (2006); http://dx.doi.org/10.1116/1.2357958 (5 pages)

Online Publication Date: 12 October 2006

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Microwave excited plasma source operating at a low pressure of 1.5 Pa was newly developed. This plasma source was successfully applied to the formation of hydrogenated microcrystalline silicon films in a glass substrate with a mixture gas of silane (SiH4), hydrogen (H2), and xenon (Xe). It was found that the crystallinity of films was dramatically improved with decreasing pressure. The crystalline fraction was evaluated to be 82% at a substrate temperature of 400 °C, a mixture gas of SiH4/H2/Xe: 5/200/30 SCCM, and a total pressure of 1.5 Pa by Raman spectroscopy. The absolute density of hydrogen atoms and the behavior of higher radicals and molecules in the mixture gas were evaluated using vacuum ultraviolet absorption spectroscopy and quadrupole mass spectrometer, respectively. H atom densities were of the order of 1011 cm−3. The fraction of H atom density increased, while higher radicals and molecules decreased with decrease in the total pressure. The increase in H atom density and decrease in higher radicals and molecules improved the crystallinity of films in low pressures below 10 Pa.
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52.77.Dq Plasma-based ion implantation and deposition
78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators
68.55.-a Thin film structure and morphology
78.40.Fy Semiconductors

Lifetime measurement of metastable fluorine atoms using electron cyclotron resonance plasma source

Masao Shimizu, Hiromasa Ohmi, Hiroaki Kakiuchi, and Kiyoshi Yasutake

J. Vac. Sci. Technol. A 24, 2133 (2006); http://dx.doi.org/10.1116/1.2357959 (6 pages)

Online Publication Date: 12 October 2006

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The authors have measured the lifetime of metastable state (3s math) of F atoms by resonant laser-induced fluorescence method. For this experiment, a special 2.45 GHz electron cyclotron resonance (ECR) plasma source, which is highly efficient in F radical generation and free from magnetic field leakage in front of the beam-emitting orifice, has been developed. Using the ECR plasma gun, the authors observed a precision fluorescence spectrum related to 3p math(F = 4)→3s math(F = 3) transition of F radicals, which made it possible to experimentally determine the longitudinal velocity distribution and the angular spread of the F radical beam. Based on these measured beam characteristics, the authors extracted a true decay curve of fluorescence intensity as a function of distance from the source and determined the lifetime of F metastable state (3s math) as 7.3±0.5 μs.
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52.50.Dg Plasma sources
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
32.50.+d Fluorescence, phosphorescence (including quenching)
32.70.Cs Oscillator strengths, lifetimes, transition moments

Influence of thermal annealing on the resistivity of titanium/platinum thin films

U. Schmid and H. Seidel

J. Vac. Sci. Technol. A 24, 2139 (2006); http://dx.doi.org/10.1116/1.2359739 (8 pages) | Cited 6 times

Online Publication Date: 12 October 2006

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In this study, the authors investigate the influence of thermal annealing up to temperatures of 700 °C on the room-temperature resistivity of electron-beam-evaporated titanium/platinum thin films. Oxidized silicon wafers are used as the substrate. The titanium has a fixed thickness of 5 nm and serves as an adhesion layer. The thickness of the platinum top is varied between 21 and 97 nm. Up to annealing temperatures of 450 °C, the film resistivity of the bilayer system is a linear correlation with the reciprocal platinum film thickness, as expected from the size effect. In this annealing regime, the change in intrinsic film stress dominates the electrical behavior. At annealing temperatures of 600 °C and above, however, the diffusion of titanium into the top layer leads to an enhanced increase in film resistivity, especially at low platinum thicknesses. The onset of plastic deformation of the platinum layer causes an additional effect that decreases the electrical conductivity above average.
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73.61.At Metal and metallic alloys
81.40.Gh Other heat and thermomechanical treatments
73.40.Ns Metal-nonmetal contacts
68.60.Bs Mechanical and acoustical properties
66.30.-h Diffusion in solids
81.40.Lm Deformation, plasticity, and creep

Thermally induced structural changes in nanoporous silicon dioxide from x-ray photoelectron spectroscopy

Martin T. K. Soh, J. H. Thomas, and Joseph J. Talghader

J. Vac. Sci. Technol. A 24, 2147 (2006); http://dx.doi.org/10.1116/1.2359734 (4 pages) | Cited 2 times

Online Publication Date: 18 October 2006

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Morphological changes due to adsorbed gases in nanoporous silicon dioxide thin films are demonstrated using in situ x-ray photoelectron spectroscopy at temperatures in the range 20 ⩽ T ⩽ 300 °C. Adsorbed hydrogen bonded water vapor is observed to relax the surface bond strain of low-temperature electron-beam deposited silicon dioxide up to 100 °C. This was determined by measuring the width of the Si 2p and O 1s photoemission peak full widths at half maximum, which are distinctly smaller for films with adsorbed water vapor than for the same films after vapor has been outgassed by heating above 100 °C. In situ heating in the range 100<T<200 °C decreases the peak width as the atoms gain sufficient energy to establish a more homogeneous local bonding environment. This process is overshadowed above 200 °C as thermally induced localized bond strains and charge inhomogeneities at the surface begin to introduce disorder, as demonstrated in the repeatable increase in peak spread with temperature for thermally grown silicon dioxide and quartz. The in vacuo peak width behavior in subsequent thermal cycles is repeatable for the nanoporous thin films. However, if the films are reexposed to atmosphere, the initial increase in peak width is seen again.
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81.05.Rm Porous materials; granular materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
61.43.Gt Powders, porous materials
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.43.Mn Adsorption kinetics

Time-resolved measurements of the E-to-H mode transition in electronegative pulse-modulated inductively coupled plasmas

Manabu Edamura, Eric C. Benck, and Yicheng Wang

J. Vac. Sci. Technol. A 24, 2151 (2006); http://dx.doi.org/10.1116/1.2359736 (8 pages) | Cited 1 time

Online Publication Date: 18 October 2006

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Time-resolved measurements of electronegative pulse-modulated inductively coupled plasmas (ICPs) were carried out using various measurement techniques. In order to explain the experimentally observed results, it is proposed that the structure of an Ar/CF4 plasma during an afterglow dynamically changes, passing through three stages when the period of the afterglow is long enough: (1) The first stage is the initial afterglow where the electron temperature suddenly decreases due to inelastic collision with CF4. Electron density decreases and the density of fluorine negative ions increases by electron attachment, but the sheath potential still exists and the negative ions are confined in the bulk plasma region. Since charge neutrality should be maintained, the density of positive ions is almost constant during this stage. (2) The second stage is the intermediate afterglow where the plasma consists mainly of negative and positive ions but sheath potentials remain, reducing the negative ion flux from the plasma. The sheath potential gradually disappears and the densities of all the charged particles (electrons and positive and negative ions) decrease because of increased loss to the wall surface. (3) The third stage is where the sheath structure has disappeared completely, and the plasma consists of mainly positive and negative ions and losses are dominated by ambipolar diffusion. The presence of these stages during the afterglow is very important in understanding the behavior of pulsed ICPs with E-to-H mode transitions. The state of an afterglow plasma at the moment power is reapplied determines the discharge characteristics of the pulsed ICPs (e.g., the appearance of an E mode, the duration of the E mode, stability of the plasma).
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Ds Electric and magnetic measurements
52.50.Dg Plasma sources
52.80.Hc Glow; corona
52.40.Kh Plasma sheaths
52.25.Fi Transport properties

New design for indentation measurement using fiber Bragg grating

Jun Chen and Mojtaba Kahrizi

J. Vac. Sci. Technol. A 24, 2159 (2006); http://dx.doi.org/10.1116/1.2360977 (5 pages)

Online Publication Date: 18 October 2006

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A new methodology to characterize mechanical properties of materials using a fiber Bragg grating is reported. A theory for the new technique to measure indentation is developed and experimental results performed by the technique are reported. The measurement range, displacement sensitivity, penetration depth, and forces against the fiber and the sample are analyzed. The load-depth curve of a typical indentation measurement was obtained. The technique has dual sensing abilities for applied force and the corresponding displacement, and it is shown that the method can be used as an instrument to characterize material surfaces. The dynamic measurement, small size sensing, simple measurement configuration, linear responsive behavior, and easy interpretation are some of the characteristics of this design.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Microstructural differences in thin film ZnGa2O4:Mn phosphor produced by differences in sputtering gas pressure

Joo Han Kim and Paul H. Holloway

J. Vac. Sci. Technol. A 24, 2164 (2006); http://dx.doi.org/10.1116/1.2359737 (8 pages) | Cited 1 time

Online Publication Date: 20 October 2006

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The authors report on the microstructural characteristics of sputter-deposited thin film ZnGa2O4:Mn phosphors, with an emphasis on the role of energetic particle bombardment. The thin film ZnGa2O4:Mn phosphors were deposited by radio frequency planar magnetron sputtering of a 2 mol % Mn-doped ZnGa2O4 target in an Ar–O2 gas mixture at gas pressures ranging from 2 to 20 mTorr. The growth rate of the ZnGa2O4:Mn films was decreased from 40 to 23 Å/min as the gas pressure was raised due to both increased gas-phase scattering as well as reduced target self-bias voltage. Owing to the thermalization of impinging energetic particles and the randomization in their incidence directions when arriving at the substrate, the ZnGa2O4:Mn films produced at an elevated gas pressure exhibited a porous composite microstructure in which larger columns consisted of bundles of smaller columns separated by voided boundaries. Energetic particle bombardment of the growing film surface at a low gas pressure yielded a densely packed zone-T-type microstructure due to porosity annihilation by knock-on processes and bombardment-enhanced adatom mobility. Atomic force microscopy and grazing incidence x-ray reflectivity data revealed that as the gas pressure was decreased from 20 to 2 mTorr, the rms surface roughness of the deposited ZnGa2O4:Mn films was reduced from 4.95 to 1.23 nm and the film density increased from 5.314 to 5.681 g/cm3, consistent with the postulated effects of energetic particle bombardment upon film microstructure.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
68.35.B- Structure of clean surfaces (and surface reconstruction)

Real-time monitoring of charge accumulation during pulse-time-modulated plasma

Hiroto Ohtake, Butsurin Jinnai, Yuya Suzuki, Shinnosuke Soda, Tadashi Shimmura, and Seiji Samukawa

J. Vac. Sci. Technol. A 24, 2172 (2006); http://dx.doi.org/10.1116/1.2362724 (4 pages) | Cited 2 times

Online Publication Date: 20 October 2006

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The authors investigated real-time monitoring of charge accumulation during pulse-time-modulated plasma processes by using their developed on-wafer monitoring chip. The charge accumulation potential between the top surface and the bottom in a SiO2 contact structure was measured during pulse-time-modulated plasma exposure with an on-wafer monitoring device. In conventional plasma with rf bias, the electron shading effect could be clearly observed as the potential difference between the wafer surface and the contact-hole bottom. Conversely, the accumulated charge in the pulse-time-modulated operation was drastically decreased. Time-resolved electron and ion flows to the SiO2 contact hole were clarified by the on-wafer monitoring. Accordingly, it was confirmed that the on-wafer monitoring is a very effective tool for investigating the local charge accumulation in actual device structures.
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73.40.Cg Contact resistance, contact potential
81.16.Rf Micro- and nanoscale pattern formation
52.77.Bn Etching and cleaning

In situ measurement of the ion incidence angle dependence of the ion-enhanced etching yield in plasma reactors

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

J. Vac. Sci. Technol. A 24, 2176 (2006); http://dx.doi.org/10.1116/1.2362725 (11 pages) | Cited 6 times

Online Publication Date: 20 October 2006

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The authors propose and demonstrate a technique to determine the ion incidence angle dependence of the ion-enhanced etching yield under realistic plasma conditions and in situ in an arbitrary plasma reactor. The technique is based on measuring the etch rate as a function of position along the walls of features that initially have nearly semicircular cross sections. These initial feature shapes can be easily obtained by wet or isotropic plasma etching of holes patterned through a mask. The etch rate as a function of distance along the feature profile provides the etching yield as a function of the ion incidence angle. The etch rates are measured by comparing digitized scanning electron micrograph cross sections of the features before and after plasma etching in gas mixtures of interest. The authors have applied this technique to measure the ion incidence angle dependence of the Si etching yield in HBr, Cl2, SF6, and NF3 plasmas and binary mixtures of SF6 and NF3 with O2. Advantages and limitations of this method are also discussed.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Thin film deposition of barium strontium oxide by rf magnetron sputtering

Yan Liu, Christopher M. Day, Scott A. Little, and Feng Jin

J. Vac. Sci. Technol. A 24, 2187 (2006); http://dx.doi.org/10.1116/1.2363400 (5 pages)

Online Publication Date: 20 October 2006

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Barium strontium oxide [(BaSr)O] thin films approximately 1 μm in thickness were deposited on tungsten substrates using rf magnetron sputter deposition for thermionic cathode applications. Three substrate temperatures ranging from 25 to 700 °C were used in the deposition processes to create oxide films with different surface morphologies and crystalline structures. The films were characterized with scanning electron microscopy and their surface morphologies were correlated to their thermionic emission properties. The results showed that the surface morphology and crystalline structure of the oxide films strongly affected the emission properties. The oxide film deposited at the lowest substrate temperature of 25 °C showed a rough surface and a crystalline structure consisting of nanograins. At higher substrate temperatures, the oxide films exhibited smooth surfaces and close-packed crystalline structures with larger grains. The work function of the oxide films was reduced and the emission current density increased as a result of the increase in the growth temperature. The (BaSr)O film made at 700 °C exhibited the lowest work function of 1.57 eV and the largest emission current density of 1.60 A/cm2 at 1198 K under an electrical field of 0.88 V/μm. The emission current density and the work function of the (BaSr)O thin film cathodes were stable over the testing period of 8 h. Compared to the traditional cathode fabrication process, which involves the coating of carbonates followed by an activation process, rf magnetron sputtering has a greater ability to control the deposition parameters, which makes it a valuable alternative technique to fabricate oxide cathodes.
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81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.66.Fn Inorganic compounds
68.35.Ct Interface structure and roughness

Vapor phase reactions in polymerization plasma for divinylsiloxane-bis-benzocyclobutene film deposition

Keizo Kinoshita, Akinori Nakano, Jun Kawahara, Nobutaka Kunimi, Yoshihiro Hayashi, Osamu Kiso, Naoaki Saito, Keiji Nakamura, and Takamaro Kikkawa

J. Vac. Sci. Technol. A 24, 2192 (2006); http://dx.doi.org/10.1116/1.2359738 (7 pages) | Cited 2 times

Online Publication Date: 25 October 2006

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Vapor phase reactions in plasma polymerization of divinylsiloxane-bis-benzocyclobutene (DVS-BCB) low-k film depositions on 300 mm wafers were studied using mass spectrometry, in situ Fourier transform infrared, and a surface wave probe. Polymerization via Diels-Alder cycloaddition reaction was identified by the detection of the benzocyclohexene group. Hydrogen addition and methyl group desorption were also detected in DVS-BCB monomer and related large molecules. The dielectric constant k of plasma polymerized DVS-BCB with a plasma source power range up to 250 W was close to ∼ 2.7 of thermally polymerized DVS-BCB, and increased gradually over 250 W. The electron density at 250 W was about 1.5×1010 cm−3. The increase of the k value at higher power was explained by the decrease of both large molecular species via multistep dissociation and incorporation of silica components into the polymer. It was found that the reduction of electron density as well as precursor residence time is important for the plasma polymerization process to prevent the excess dissociation of the precursor.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
82.35.-x Polymers: properties; reactions; polymerization
52.77.Dq Plasma-based ion implantation and deposition
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)

Structural, electrical, optical, and photoelectrochemical properties of thin titanium oxinitride films (TiO2−2xNx with 0 ⩽ x ⩽ 1)

U. Koslowski, K. Ellmer, P. Bogdanoff, T. Dittrich, T. Guminskaya, and H. Tributsch

J. Vac. Sci. Technol. A 24, 2199 (2006); http://dx.doi.org/10.1116/1.2362740 (7 pages) | Cited 6 times

Online Publication Date: 25 October 2006

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Nanocrystalline titanium oxinitride (TiO2−2xNx) thin films (0 ⩽ x ⩽ 1) were prepared by reactive dc magnetron sputtering from a titanium target in an argon-oxygen-nitrogen atmosphere. By increasing the reactive gas component nitrogen the phases changed from TiO2 to TiO2−2xNx and finally to TiN. The reactively sputtered films were characterized by elastic recoil detection analysis, Raman spectroscopy, and resistivity measurements. The crystallographic structures of TiO2 were maintained up to a nitrogen concentration of about 20 at. %; however, the crystallite size decreased significantly and a transition from the low-temperature anatase to the high-temperature rutile phase of TiO2 occurred. Optical transmission measurements revealed that the indirect energy band gap can be reduced from 3.2 to 2.6 eV for nitrogen concentrations up to 20 at. %. The film properties for photocatalytic water oxidation were investigated by differential electrochemical mass spectroscopy. While the photoactivity in the visible increases, the overall photoelectrochemical activity appears to be deteriorated significantly by nitrogen doping, most probably due to the formation of defect states near to the valence band of TiO2.
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78.66.Nk Insulators
73.61.Ng Insulators
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
78.30.Hv Other nonmetallic inorganics
64.70.K- Solid-solid transitions

Deposition profile of Ti film inside a trench and its correlation with gas-phase ionization in high-pressure magnetron sputtering

N. Nafarizal, N. Takada, K. Nakamura, Y. Sago, and K. Sasaki

J. Vac. Sci. Technol. A 24, 2206 (2006); http://dx.doi.org/10.1116/1.2363999 (6 pages) | Cited 9 times

Online Publication Date: 25 October 2006

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This article reports the relationship between the degree of ionization of Ti in the gas phase and the thickness profile of Ti film inside a trench in magnetron sputtering deposition. A conventional magnetron sputtering plasma source was used for depositing Ti films inside trenches formed on rf-biased SiO2 substrates. It was found that a high bottom coverage was obtained when a high gas pressure and a long distance between the target and the substrate were employed for the deposition. On the other hand, at a short distance between the target and the substrate, the bottom coverage was small and was almost independent of the gas pressure. The deposition profile was compared with the spatial distributions of Ti and Ti+ densities measured by laser-induced fluorescence (LIF) imaging spectroscopy. The LIF results revealed that the density ratio of Ti+ to Ti in the downstream region increased with the gas pressure up to 0.3, while in the upstream region, it was small (<0.05) and was roughly constant with the gas pressure. In the case with the enhanced density ratio of 0.3, the flux ratio of Ti+ to Ti was estimated to be 4.4. Hence, it was concluded that, with a high gas pressure and a long distance between the target and substrate, the deposition profile with a high bottom coverage was obtained by accelerating Ti+ toward the bottom of the trench. The high-pressure magnetron sputtering discharge is useful for enhancing the degree of ionization and the bottom coverage.
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81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
52.77.Dq Plasma-based ion implantation and deposition
85.40.Sz Deposition technology

Effects of the growth conditions on the roughness of amorphous hydrogenated carbon films deposited by plasma enhanced chemical vapor deposition

G. Capote, R. Prioli, and F. L. Freire

J. Vac. Sci. Technol. A 24, 2212 (2006); http://dx.doi.org/10.1116/1.2362723 (5 pages) | Cited 3 times

Online Publication Date: 27 October 2006

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The surface roughness and scaling behavior of a‐C:H films deposited by plasma enhanced chemical vapor deposition from CH4–Ar mixtures were studied using atomic force microscopy. Raman spectroscopy gives some insights about the film microstructure. The film surface roughness is shown to decrease with the increase of deposition negative self-bias, while the presence of Ar ions enhances this effect. An analysis of the film surface and scaling behavior suggests that there is a transition of the mechanism of the film growth from a random deposition with surface diffusion process to a thermal spike based process that occurs upon the increase of the negative self-bias voltage and the argon bombardment.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation
68.55.A- Nucleation and growth
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Measurement of desorbed products during organic polymer thin film etching by plasma beam irradiation

Kazuaki Kurihara, Kazuhiro Karahashi, Akihiro Egami, and Moritaka Nakamura

J. Vac. Sci. Technol. A 24, 2217 (2006); http://dx.doi.org/10.1116/1.2364000 (6 pages) | Cited 4 times

Online Publication Date: 27 October 2006

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The authors investigated the etching characteristics of three kinds of methacrylate polymer films, which have the same main chain but with different side chains, using a plasma beam irradiation apparatus. The polymers are polytbutylmethacrylate, polybenzylmethacrylate, and polycyclohexylmethacrylate. The major desorbed products during nitrogen plasma beam etching were found to be HCN and C2N2 for all methacrylate polymer films. The desorbed products originating from the polymer structure, namely, the main chain and the side chain, were hardly observed. The energy distributions of desorbed products were mainly composed of Maxwell-Boltzmann distribution with a small component of collision cascade distribution for all three polymers and were slightly dependent on the ion energy. It is concluded that chemical sputtering, which can be defined as the production of weakly bound species by ion bombardment, followed by thermal desorption, is the significant ion induced mechanism of organic polymer etching.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
68.43.Mn Adsorption kinetics
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Heat trapping for fast pumping of very hot gases

E. J. Petit

J. Vac. Sci. Technol. A 24, 2223 (2006); http://dx.doi.org/10.1116/1.2345647 (6 pages)

Online Publication Date: 8 November 2006

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Industrial treatments of surfaces can take advantage of process switching between high pressure and low pressure (or vacuum), both at high temperatures. For the optimization of the industrial throughput, as well as for surface quality and thermal efficiency, it may be practical to avoid a delay in cooling the gas before pumping. Now, safety requires precaution in order to avoid ignition of oil-sealed mechanical pumps when very hot gas must be pumped close to atmospheric pressure. This article searches for a mechanism to achieve fast cooling before gases enter the pumping system. The author suggests that heat can be trapped momentarily during pumping at high pressure, and that the stored heat can be dissipated over a longer period of time after pumping. This concept is simple and practical; it provides a low cost solution for many cases. It is relevant when gases are pumped transiently. Reliability of this solution depends on scaling the heat trap to the maximum temperature and volume of gases, as well as to the pumping speed to be achieved. Design considerations are of the utmost importance. In particular, mass and exchange area of the heat sink are essential parameters. This article proposes simple mathematical tools for safe dimensioning. Model exploitation is illustrated on an example considering pumping a 2 m3 chamber filled to atmospheric pressure by a gas at 500 or 800 °C. The author assumes the vessel is pumped in ∼ 2–10 min by a “roots” type pump connected in series with an oil-sealed mechanical pump (60–350 m3/h). Model predictions indicate that a spiral rolled stainless steel sheet is more efficient than a collection of tubes as a heat sink although a trap made of tubes provides a cheaper apparatus.
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47.27.te Turbulent convective heat transfer
51.10.+y Kinetic and transport theory of gases
47.85.M- Material processing flows; industrial applications
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