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May 2008

Volume 26, Issue 3, pp. 313-557

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Role of oxygen impurities in etching of silicon by atomic hydrogen

Stan Veprek, Chunlin Wang, and Maritza G. J. Veprek-Heijman

J. Vac. Sci. Technol. A 26, 313 (2008); http://dx.doi.org/10.1116/1.2884731 (8 pages) | Cited 4 times

Online Publication Date: 26 March 2008

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In a pure-hydrogen glow discharge plasma, the etch rate of silicon increases with increasing temperature up to about ≥ 1100 Å/s at 60–80 °C and, upon a further increase of the temperature, etch rate strongly decreases, showing Arrhenius-like dependence with negative apparent activation energy of −1.5 kcal/mol. When the Si sample is at the floating potential, oxygen impurities of ≥ 10 at. ppm strongly decrease the etch rate. At more than 70 ppm of oxygen, the etching stops. Oxygen adsorbed on the Si surface can be removed by ion bombardment when negative potential is applied to the Si sample and the Si is then etched chemically by H atoms. The etching by atomic hydrogen is isotropic in an oxygen-free system. A controllable addition of a few ppm of oxygen in combination with negative bias of the Si sample results in highly anisotropic etching with thin oxide acting as side-wall passivation.
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81.65.Cf Surface cleaning, etching, patterning
52.80.Hc Glow; corona
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
61.72.S- Impurities in crystals

On the mechanism of tritium desorption from stainless steel

K. Akaishi, Y. Torikai, D. Murata, R.-D. Penzhorn, K. Watanabe, and M. Matsuyama

J. Vac. Sci. Technol. A 26, 321 (2008); http://dx.doi.org/10.1116/1.2889391 (7 pages)

Online Publication Date: 26 March 2008

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Stainless-steel specimens (15×15×0.5 mm3) containing homogeneously distributed tritium were used for the experiments. To investigate the fate of tritium in the surface region, about 70 μm were chemically etched and the regrowth of tritium on the top surface layer determined as function of time by β-ray-induced x-ray spectrometry. Simultaneously, the specimen was flushed with an argon gas stream at ambient temperature and the released tritium collected in water bubblers. The chronically liberated tritium retained in the bubblers was quantified in regular intervals using a liquid-scintillation counting technique. It was found to consist predominantly of tritiated water (99%); the rest probably being tritium-containing hydrogen. In this work, a model for the transport of hydrogen is proposed that allows quantitative evaluation of the experimental results. It is demonstrated that the numerical simulation accurately predicts the amount of tritium progressively trapped on the surface and that slowly released at ambient temperature from the bulk of the stainless-steel material.
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68.43.Nr Desorption kinetics
81.65.Cf Surface cleaning, etching, patterning
66.30.Fq Self-diffusion in metals, semimetals, and alloys

Influence of the microstructure on steel hardening in pulsed plasma nitriding

E. A. Ochoa and C. A. Figueroa

J. Vac. Sci. Technol. A 26, 328 (2008); http://dx.doi.org/10.1116/1.2889395 (5 pages)

Online Publication Date: 26 March 2008

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The plasma technologies are widely used in metal surface engineering processes. Basically, these treatments improve the mechanical, tribological, and chemical properties of the material such as wear resistance, hardness, fatigue resistance, friction, and corrosion resistance. In this work, a comprehensive study of the influence of the microstructure on hardness of AISI P20 steel treated at different temperatures and times by pulsed plasma nitriding is reported. The processes were done by using a pulsed plasma industrial system. The samples were characterized by nano-indentation (hardness), x-ray diffraction (XRD), scanning electron microscopy (SEM), and x-ray dispersion spectroscopy (EDS). At lower treatment temperatures (360 °C), a high density of small lamellar precipitates, constituted by more ε-Fe2–3N phase than γ′-Fe4N phase, is formed. At intermediate treatment temperatures (480 °C), big lamellar precipitates, constituted by more γ′-Fe4N phase than ε-Fe2−3N phase, are formed at grain boundary. At higher treatment temperatures (520 °C), the nitrided layer does not contain lamellar precipitates and it is only constituted by α-Fe phase saturated in nitrogen. Hardness depends on size, shape, and distribution of precipitates and crystalline phases (microstructure). The higher hardness values are obtained when more and smaller lamellar precipitates are presented and constituted by more ε-Fe2−3N phase.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
81.40.Pq Friction, lubrication, and wear
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.65.Kn Corrosion protection
81.30.Mh Solid-phase precipitation
61.72.Mm Grain and twin boundaries

Experimental study of Cr/Sc multilayer mirrors for the nitrogen Kα-emission line

Aurélie Hardouin, Franck Delmotte, Marie Françoise Ravet, Françoise Bridou, Arnaud Jerome, Françoise Varniere, Claude Montcalm, Sébastien Hedacq, Eric Gullikson, and Pascal Aubert

J. Vac. Sci. Technol. A 26, 333 (2008); http://dx.doi.org/10.1116/1.2891248 (5 pages)

Online Publication Date: 26 March 2008

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The authors present an experimental study of Cr/Sc multilayer mirrors optimized for the detection of the nitrogen Kα-emission line (λ = 3.16 nm) at a grazing incidence around 23°, for electron probe microanalysis applications. The multilayers were deposited onto silicon substrates using a dc magnetron sputtering system. They were characterized with grazing incidence copper Kα x-ray reflectometry and atomic force microscopy, as well as with at-wavelength reflectometry using synchrotron radiation. These various characterization methods pointed out that the interfacial roughness of these multilayers increases drastically with the number of bilayers. Growth parameters were then optimized, and it is shown that the structure and reflectivity of such multilayers can be considerably improved by optimizing the sputter gas pressure during the deposition process. Reflectivity higher than 37% were measured at 22.3° grazing angle for the nitrogen Kα-emission line.
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68.65.Ac Multilayers
81.15.Cd Deposition by sputtering
82.80.-d Chemical analysis and related physical methods of analysis

Preparation of TiO2 thin films on the inner surface of a quartz tube using atmospheric-pressure microplasma

Hiroyuki Yoshiki and Taku Saito

J. Vac. Sci. Technol. A 26, 338 (2008); http://dx.doi.org/10.1116/1.2891251 (6 pages) | Cited 1 time

Online Publication Date: 26 March 2008

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Titanium dioxide (TiO2) thin films were prepared on the inner surface of a quartz tube, with inner and outer diameters of 1 and 3 mm, respectively, using plasma-enhanced chemical vapor deposition with titanium tetraisopropoxide and oxygen (O2) as reactants and helium as the carrier gas at atmospheric pressure. A microplasma was generated inside the tube by rf (13.56 MHz) excitation using externally attached parallel-plate electrodes. The characteristics of the deposited films were examined by scanning electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction. A typical as-deposited film had an amorphous structure with a smooth surface and was transparent. With increasing O2 concentration in the plasma gas phase, the deposited film surface was covered with a large number of TiO2 nanoparticles. However, the deposited films were a mixture of TiO2 and amorphous carbon and showed rough surface in the absence of O2 in the source gas. The effects of the O2 concentration in the plasma gas on the characteristics of the deposited TiO2 films are discussed on the basis of the analysis of the gas species generated in the plasma using optical emission spectroscopy.
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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.J- Morphology of films
68.47.Gh Oxide surfaces
61.43.Er Other amorphous solids
78.66.Jg Amorphous semiconductors; glasses

Effect of gas mixing ratio on etch behavior of ZrO2 thin films in BCl3/He inductively coupled plasma

Mansu Kim, Nam-Ki Min, Sun Jin Yun, Hyun Woo Lee, Alexander Efremov, and Kwang-Ho Kwon

J. Vac. Sci. Technol. A 26, 344 (2008); http://dx.doi.org/10.1116/1.2891255 (8 pages) | Cited 1 time

Online Publication Date: 26 March 2008

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This article reports a study carried out on a model-based analysis of the etch mechanism for ZrO2 thin films in a BCl3/He inductively coupled plasma. It was found that an increase in the He mixing ratio at a fixed gas pressure and input power results in an increase in the ZrO2 etch rate, which changes from 36 to 57 nm/min for 0–83% He. Langmuir probe diagnostics and zero-dimensional plasma modeling indicated that both plasma parameters and active species kinetics were noticeably influenced by the initial composition of the BCl3/He mixture, resulting in the nonmonotonic or nonlinear behaviors of species densities. Using the model-based analysis of etch kinetics, it was demonstrated that the behavior of the ZrO2 etch rate corresponds to the ion-flux-limited etch regime of the ion-assisted chemical reaction.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
52.70.Ds Electric and magnetic measurements
52.25.Dg Plasma kinetic equations
52.65.-y Plasma simulation
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

On the gas species dependence of Pirani vacuum gauges

Karl Jousten

J. Vac. Sci. Technol. A 26, 352 (2008); http://dx.doi.org/10.1116/1.2897314 (8 pages)

Online Publication Date: 26 March 2008

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The dependence of the readings of four different Pirani vacuum gauges on nine different gas species was investigated. It was found that the gas species dependence varied from gauge to gauge so that in general only an approximate correction factor for a specific gas species can be given for this type of vacuum gauge. A Pirani gauge produced by microstructuring methods showed a broader measurement range than conventionally produced gauges. By comparing experimental with theoretical data, it was possible to give upper limits of the thermal accommodation coefficients of the nine gas species on the technical surfaces of oxidized tungsten and silicon within the gauges.
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07.30.Dz Vacuum gauges
05.70.Ce Thermodynamic functions and equations of state

Study of tungsten oxidation in O2/H2/N2 downstream plasma

Songlin Xu and Li Diao

J. Vac. Sci. Technol. A 26, 360 (2008); http://dx.doi.org/10.1116/1.2897316 (5 pages) | Cited 2 times

Online Publication Date: 26 March 2008

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The surface oxidation of tungsten is a serious issue in plasma processing of advanced integrated-circuit devices where tungsten is being used as a gate electrode. In this article, we study tungsten oxidation in O2/H2/N2 downstream plasma at a temperature ⩽ 300 °C. The results show that oxidation occurs rapidly in O2 downstream plasma to form stable WO3. However, oxidation can be reduced effectively by adding H2 and totally suppressed when H2 concentration in the gas feed reaches a certain low level at which the plasma is still oxygen dominant. Tungsten oxidation increases significantly with sample temperature and exposure time in O2 downstream plasma. However, H2 addition reduces both temperature and time dependences due to the coexistence and competition of oxidation and reduction processes. When N2 is also added, the efficiency of H2 in O2 downstream plasma in controlling tungsten oxidation is lowered. The findings may provide effective approaches to various applications of selective oxidation over tungsten, such as photoresist stripping and polysilicon oxidation on tungsten gate structures.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Development of a compact vacuum- and hydrogen-annealing machine for surface transformation of silicon and its applications to micro-optical devices

Yoshiaki Kanamori, Kenichi Douzono, Shinya Fujihira, and Kazuhiro Hane

J. Vac. Sci. Technol. A 26, 365 (2008); http://dx.doi.org/10.1116/1.2897317 (5 pages) | Cited 2 times

Online Publication Date: 26 March 2008

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The authors developed a compact vacuum- and hydrogen-annealing machine to transform and smooth silicon surfaces for silicon microoptical devices. Two kinds of configurations, named sealing type and flowing type, were evaluated. The sealing type configuration was designed to anneal a sample inside a H2 gas environment contained within a quartz tube. On the other hand, the flowing type configuration was designed to anneal the sample using a flowing H2 gas environment. The machine sizes were 1.6 m in width, 0.55 m in depth, and 1.3 m in height. Control ranges of temperature and pressure were between 20 °C and 1300 °C and between 4.1×10−7 and 760 Torr, respectively. Using the flowing type configuration, the samples were successfully smoothed at conditions of H2 partial pressure of 50 Torr, temperature of 1230 °C, H2 gas flow rate of 1 slm, and annealing time of 11 min. By transforming the surface, microlenslike structures with the size of the order of several micrometers and a sinusoidal grating were also fabricated from cylindrical pillars and a lamellar grating, respectively. The authors measured the surface roughness on the samples before and after annealing, and it was obviously decreased after annealing for all of the measured samples.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.35.Rh Phase transitions and critical phenomena
42.79.Dj Gratings
68.35.bg Semiconductors

Oxidation of silicon nanowires for top-gated field effect transistors

Bangzhi Liu, Yanfeng Wang, Tsung-ta Ho, Kok-Keong Lew, Sarah M. Eichfeld, Joan M. Redwing, Theresa S. Mayer, and Suzanne E. Mohney

J. Vac. Sci. Technol. A 26, 370 (2008); http://dx.doi.org/10.1116/1.2899333 (5 pages) | Cited 4 times

Online Publication Date: 26 March 2008

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The oxidation of unintentionally doped p-type silicon nanowires grown by the vapor-liquid-solid (VLS) method and their integration into top-gated field effect transistors is reported. Dry thermal oxidation of as-grown silicon nanowires with diameters ranging from 20 to 400 nm was carried out at 700 and 900 °C with or without the addition of a chlorinated gas source. The oxidation rate was strongly dependent on the as-grown nanowire diameter, with the large-diameter nanowires oxidizing up to five times faster than the smallest nanowires at 900 °C. At each diameter, the addition of trichloroethane (TCA) enhanced the rate compared to oxidation in pure O2. Top-gated field effect transistors fabricated from nanowires oxidized at 700 °C had significantly less hysteresis in their subthreshold properties when TCA was added, but oxidation at 900 °C with or without TCA provided hysteresis-free devices with improved subthreshold slope. Such enhancements in the electrical properties are expected based on advances in planar silicon process technology and emphasizes the importance of incorporating these techniques for VLS-grown nanowire devices.
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85.35.−p
73.63.Bd Nanocrystalline materials
81.65.Mq Oxidation

Thermal conductivity of semi-insulating, p-type, and n-type GaN films on sapphire

K. Jagannadham, E. A. Berkman, and N. Elmasry

J. Vac. Sci. Technol. A 26, 375 (2008); http://dx.doi.org/10.1116/1.2899379 (5 pages) | Cited 1 time

Online Publication Date: 26 March 2008

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The thermal conductivity of undoped, n-type, and p-type GaN films deposited on (0001) substrates of sapphire was measured by the 3-ω method in the temperature range between 215 and 300 K. The thickness, thermal conductivity, and heat capacity of the individual layers were used to simulate the experimental value of the increment in temperature of the heater using a multilayer model. The thermal conductivity of undoped GaN film was found to be much higher than that of p-type film. Also, the thermal conductivity of n-type GaN film was slightly smaller than that of p-type film. Modeling of the temperature dependence of the thermal conductivity in the films showed that phonon-dopant and three-phonon umklapp scattering are important. Smaller thickness and hence smaller volume fraction of the film with lower dislocation density was also found to be responsible for lower thermal conductivity in n- and p-type GaN films.
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66.70.Df Metals, alloys, and semiconductors
65.40.Ba Heat capacity
63.22.Dc Free films
63.20.kp Phonon-defect interactions
61.72.Lk Linear defects: dislocations, disclinations
68.60.Dv Thermal stability; thermal effects

Preparation of α-Al2O3 thin films by electron cyclotron resonance plasma-assisted pulsed laser deposition and heat annealing

D. Yu, Y. F. Lu, N. Xu, J. Sun, Z. F. Ying, and J. D. Wu

J. Vac. Sci. Technol. A 26, 380 (2008); http://dx.doi.org/10.1116/1.2899569 (5 pages) | Cited 1 time

Online Publication Date: 26 March 2008

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Optically transparent α-Al2O3 thin films were prepared on Si(100) substrates by electron cyclotron resonance (ECR) plasma-assisted pulsed laser deposition followed by heat annealing. Oxygen plasma produced through ECR microwave discharge was used to assist reactive deposition of amorphous aluminum oxide thin films from metallic aluminum and the deposited films were then annealed in air at temperatures ranging from 500 to 1100 °C. The as-deposited and heat-annealed films were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction analysis. The as-deposited films exhibit an amorphous structure, undergo a phase transition upon heat annealing, and convert to α form of Al2O3 with rhombohedral crystalline structure after annealing at 1100 °C. A SiO2 layer is also found to form between the aluminum oxide film and the Si substrate after the samples were annealed above 700 °C. Optical characterization reveals that aluminum oxide films deposited on sapphire substrates under the same deposition conditions are transparent from ultraviolet to near-infrared regions, and the transparency increases over 10% for the α-Al2O3 films crystallized through annealing at 1100 °C as compared with that of the as-deposited films.
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68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
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
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Db Elemental semiconductors and insulators

Dry etching of SiGe alloys by xenon difluoride

G. Xuan, T. N. Adam, P.-C. Lv, N. Sustersic, M. J. Coppinger, J. Kolodzey, J. Suehle, and E. Fitzgerald

J. Vac. Sci. Technol. A 26, 385 (2008); http://dx.doi.org/10.1116/1.2891245 (4 pages) | Cited 3 times

Online Publication Date: 4 April 2008

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Dry etching with xenon difluoride (XeF2) is a well-known process for the isotropic removal of silicon. The etching of silicon-germanium alloys with XeF2, however, has not yet been investigated. Here, the XeF2 dry etching of SiGe alloys was characterized versus composition and XeF2 partial pressures. It was found that the etch rates showed a strong dependence on Ge content of the etched materials. The roughness of the etched surfaces was also investigated. This study provides etch rates versus process conditions and etched surface roughness, which are useful for accurately fabricating SiGe-based structures and devices.
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81.65.Cf Surface cleaning, etching, patterning
68.47.Fg Semiconductor surfaces

Tin removal from extreme ultraviolet collector optics by inductively coupled plasma reactive ion etching

H. Shin, S. N. Srivastava, and D. N. Ruzic

J. Vac. Sci. Technol. A 26, 389 (2008); http://dx.doi.org/10.1116/1.2899332 (10 pages) | Cited 1 time

Online Publication Date: 4 April 2008

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Tin (Sn) has the advantage of delivering higher conversion efficiency compared to other fuel materials (e.g., Xe or Li) in an extreme ultraviolet (EUV) source, a necessary component for the leading next generation lithography. However, the use of a condensable fuel in a lithography system leads to some additional challenges for maintaining a satisfactory lifetime of the collector optics. A critical issue leading to decreased mirror lifetime is the buildup of debris on the surface of the primary mirror that comes from the use of Sn in either gas discharge produced plasma (GDPP) or laser produced plasma (LPP). This leads to a decreased reflectivity from the added material thickness and increased surface roughness that contributes to scattering. Inductively coupled plasma reactive ion etching with halide ions is one potential solution to this problem. This article presents results for etch rate and selectivity of Sn over SiO2 and Ru. The Sn etch rate in a chlorine plasma is found to be much higher (of the order of hundreds of nm/min) than the etch rate of other materials. A thermally evaporated Sn on Ru sample was prepared and cleaned using an inductively coupled plasma etching method. Cleaning was confirmed using several material characterization techniques. Furthermore, a collector mock-up shell was then constructed and etching was performed on Sn samples prepared in a Sn EUV source using an optimized etching recipe. The sample surface before and after cleaning was analyzed by atomic force microscopy, x-ray photoelectron spectroscopy, and Auger electron spectroscopy. The results show the dependence of etch rate on the location of Sn samples placed on the collector mock-up shell.
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81.65.Cf Surface cleaning, etching, patterning
68.35.bg Semiconductors
68.35.bd Metals and alloys
79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Characterization of high quality InN grown on production-style plasma assisted molecular beam epitaxy system

I. Gherasoiu, M. O’Steen, T. Bird, D. Gotthold, A. Chandolu, D. Y. Song, S. X. Xu, M. Holtz, S. A. Nikishin, and W. J. Schaff

J. Vac. Sci. Technol. A 26, 399 (2008); http://dx.doi.org/10.1116/1.2899412 (7 pages) | Cited 4 times

Online Publication Date: 4 April 2008

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In this work, the authors report step-flow growth mode of InN on [0001] oriented GaN templates, using a production-style molecular beam epitaxy system, Veeco GEN200®, equipped with a plasma source. Using adaptive growth conditions, they have obtained a surface morphology that exhibits the step-flow features. The root mean squared roughness over an area of 5×5 μm2 is 1.4 nm with monolayer height terrace steps (0.281 nm), based on atomic force microscopy. It has been found that the presence of In droplets leads to defective surface morphology. From x-ray diffraction, they estimate edge and screw dislocation densities. The former is dominant over the latter. Micro-Raman spectra reveal narrow E22 phonon lines consistent with excellent crystalline quality of the epitaxial layers. The Hall mobility of 1 μm thick InN layers, grown in step-flow mode, is slightly higher than 1400 cm2/V s, while for other growth conditions yielding a smooth surface with no well-defined steps, mobility as high as 1904 cm2/V s at room temperature has been measured. The samples exhibit high intensity photoluminescence (PL) with a corresponding band edge that shifts with free carrier concentration. For the lowest carrier concentration of 5.6×1017 cm−3, they observe PL emission at ∼ 0.64 eV.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
52.77.-j Plasma applications
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
78.55.Cr III-V semiconductors

Experimental study of spatial nonuniformities in 100 MHz capacitively coupled plasma using optical probe

V. N. Volynets, A. G. Ushakov, D. Sung, Y. N. Tolmachev, V. G. Pashkovsky, J. B. Lee, T. Y. Kwon, and K. S. Jeong

J. Vac. Sci. Technol. A 26, 406 (2008); http://dx.doi.org/10.1116/1.2899413 (10 pages) | Cited 3 times

Online Publication Date: 4 April 2008

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Plasma spatial nonuniformities in the 100 MHz rf driven capacitively coupled reactor used for reactive ion etching of 300 mm substrates were experimentally studied using a linear scanning optical emission spectroscopy probe. Radial profiles of plasma emission intensity were measured both in argon and fluorocarbon-containing gas mixtures in the pressure interval of 10–80 mTorr and the rf power range of 500–1250 W. It was demonstrated that the plasma emission profiles strongly depend on the working gas composition and pressure. The profiles have a bell-like shape at pressures about 10 mTorr for all gases. As the pressure increases, the profile shape becomes more complex with the central and peripheral peaks, and the amplitudes of the peaks strongly depend on the working gas composition. It is suggested that the emission profiles show plasma spatial nonuniformities that can influence the etching rate profiles obtained with such systems. According to the existing theoretical models, the most probable reasons for these plasma nonuniformities are charged particle radial diffusion at low pressures (about 10 mTorr), as well as the standing wave and skin and edge effects at higher pressures. Using the experimental emission profiles, the working conditions have been found that allow one to achieve the most uniform plasma for discharges in argon and fluorocarbon-containing gas mixtures.
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52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Fi Transport properties

Preparation and microstructural characterization of TiC and Ti0.6W0.4/TiC0.6 composite thin films obtained by activated reactive evaporation

J. A. Montes de Oca, Y. LePetitcorps, J.-P. Manaud, and J. R. Vargas García

J. Vac. Sci. Technol. A 26, 416 (2008); http://dx.doi.org/10.1116/1.2899457 (6 pages)

Online Publication Date: 4 April 2008

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Titanium carbide-based coatings were deposited on W substrates at a high coating growth rate by activated reactive evaporation at 500 and 600 °C in a L560 Leybold system using propene as reactive atmosphere. The crystal structure, lattice parameter, preferred orientation, and grain size of the coatings were determined by x-ray diffraction technique using Cu Kα. The analysis of the coating morphology was performed by scanning electron microscopy (SEM), and the composition of the films was analyzed by Auger electron spectroscopy and electron-probe microanalysis. Experimental results suggested that temperature was one of the most important parameters in the fabrication of stoichiometric TiC coatings. Thus, TiC coatings were obtained at 600 °C, whereas TiC0.6 nonstoichiometric coatings codeposited with a free Ti phase were obtained at 500 °C, giving rise to the formation of a composite thin film. After annealing at 1000 °C, the stoichiometric films remained stable, but a crack pattern was formed over the entire coating surface. In addition, Ti0.6W0.4/TiC0.6 composite thin coatings were obtained for the films synthesized at 500 °C. The formation of a Ti0.6W0.4 ductile phase in the presence of a TiC0.6 phase was responsible to avoid the coating cracking.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.05.Mh Cermets, ceramic and refractory composites
68.55.J- Morphology of films
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Sputtering rate of micromilling on water ice with focused ion beam in a cryogenic environment

Jing Fu, Sanjay B. Joshi, and Jeffrey M. Catchmark

J. Vac. Sci. Technol. A 26, 422 (2008); http://dx.doi.org/10.1116/1.2902962 (8 pages) | Cited 1 time

Online Publication Date: 4 April 2008

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The use of focused ion beam (FIB) milling in a cryogenic environment provides an alternative to cryomicrotome for creating submicron sections of frozen hydrated samples. Although FIB milling has been widely implemented to sculpt inorganic sample sections for analysis such as transmission electron microscopy, the application of this technique to frozen biological samples has scarcely begun. The interactions of gallium ions used in FIB with water ice as the target are still not well understood, impeding the development of this technique for routine biological analysis. In this research, amorphous water ice samples are prepared by both vapor deposition and plunge freezing, and the sputtering yield is studied based on a number of process parameters, including ion energy, temperature, and ion current. Results show that sputtering of water ice by gallium ions is a compound process of nuclear sputtering and electronic sputtering. Analytical models, originally limited to astrophysics, are adopted in this study to predict the sputtering yield of water ice by FIB. The parameters for gallium ions at keV range are estimated and validated based on the experimental data. Temperature dependence of sputtering yield is also observed in the range between 83 and 123 K, in which significant increase of sputtering yield occurs when the temperature approaches 123 K. Sputtering yield is not significantly affected by variation of the ion current as shown by the data. Based on these results, the process parameters involved can be characterized, and feasible settings can be developed to facilitate reproducibility and ultimately the widespread implementation of FIB to biological sample preparation.
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68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
81.20.Wk Machining, milling

Tungsten atomic layer deposition on cobalt nanoparticles

C. A. Wilson, D. N. Goldstein, J. A. McCormick, A. W. Weimer, and S. M. George

J. Vac. Sci. Technol. A 26, 430 (2008); http://dx.doi.org/10.1116/1.2902956 (8 pages) | Cited 2 times

Online Publication Date: 8 April 2008

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Tungsten (W) atomic layer deposition (ALD) was performed on cobalt (Co) nanoparticles using WF6 and Si2H6 as reactants. A variety of techniques were then applied to analyze both the Co nanoparticles and flat Co substrates after W ALD. Analysis of the W ALD-coated Co nanoparticles is complicated because a CoO layer may exist on the Co nanoparticles and a WO3 layer may be present on the W ALD coating. LECO measurements quantified the oxygen weight percent in the W ALD-coated Co nanoparticles. The oxygen weight percent decreased with increasing number of W ALD AB cycles. To determine the location of this oxygen, x-ray reflectivity (XRR) investigations measured the WO3 film thickness on flat W ALD films. The XRR measurements yielded a WO3 film thickness on flat W ALD films of ∼ 20 Å. X-ray photoelectron spectroscopy (XPS) studies also quantified the relative oxygen abundance at the W/Co interface for W ALD on flat Co films. The XPS measurements revealed that nearly all the oxygen was in the WO3 layer on the W ALD film. Only an immeasurably small amount of oxygen was bonded as CoO at the W/Co interface. To determine the thickness of W ALD film on the Co nanoparticle, surface profilometry of W ALD on flat Co substrates measured a W ALD growth rate of 3.9 Å per AB cycle. A geometric model was then constructed to incorporate the information from all the measurements on Co nanoparticles and flat Co substrates. Excellent agreement between the geometrical model and the oxygen weight percent versus the number of W ALD cycles was obtained when the CoO thickness was negligible and the WO3 thickness on the W ALD layer on the Co nanoparticles was 28.5 Å. This agreement indicates that the details of ALD on nanoparticles can be unraveled by a concert of techniques even when interfacial layers can form due to the high reactivity of nanoparticles. The W ALD-coated Co nanoparticles may be useful in fabricating WC–Co hardmetals with enhanced mechanical properties.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.jd Thickness
68.55.at Other materials
79.60.Jv Interfaces; heterostructures; nanostructures
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Mechanical properties of amorphous hydrogenated carbon films fabricated on polyethylene terephthalate foils by plasma immersion ion implantation and deposition

Jing Li, Xiubo Tian, Shiqin Yang, Paul K. Chu, and Ricky K. Y. Fu

J. Vac. Sci. Technol. A 26, 438 (2008); http://dx.doi.org/10.1116/1.2891253 (6 pages)

Online Publication Date: 10 April 2008

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Amorphous hydrogenated carbon (a-C:H) films have been deposited on polyethylene terephthalate by plasma immersion ion implantation and deposition. The influence of deposition parameters such as gas pressure, bias voltage, and nitrogen incorporation on the mechanical properties of the a-C:H films are investigated. X-ray photoelectron spectroscopy reveals that the ratio of sp3 to sp2 is 0.24 indicating that the film is mainly composed of graphitelike carbon. Nanoindentation tests disclose enhanced surface hardness of ∼ 6 GPa. The friction coefficient of the film deposited at higher gas pressure, for instance, 2.0 Pa, is lower than that of the film deposited at a lower pressure such as 0.5 Pa. The films deposited using a low bias voltage tend to fail easily in the friction tests and nitrogen incorporation into the a-C:H films decreases the friction coefficient. Mechanical folding tests show that deformation failure is worse on a thinner a-C:H film.
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62.20.−x
52.77.Dq Plasma-based ion implantation and deposition
62.20.Qp Friction, tribology, and hardness
81.05.U- Carbon/carbon-based materials

Multilayer transparent electrode consisting of silver alloy layer and metal oxide layers for organic luminescent electronic display device

Katsuhiko Koike and Shin Fukuda

J. Vac. Sci. Technol. A 26, 444 (2008); http://dx.doi.org/10.1116/1.2897315 (11 pages) | Cited 1 time

Online Publication Date: 10 April 2008

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A transparent electrode for an organic luminescent electronic display (OLED) requires higher transmittance and higher electric conductivity to reduce the power consumption, in order that more of the current injected into the display results in luminescence. The authors made transparent conductive multilayer coatings including layers of silver alloy with 1 wt % of palladium (Pd) and 1 wt % of copper (Cu) (APC) and transparent metal oxide thin film layers for the transparent electrode of an OLED. Indium tin oxide (ITO) and zinc aluminum oxide (AZO) were used as the transparent metal oxides. A multilayer transparent electrode consisting of ITO/APC/ITO and one of AZO/APC/AZO prepared by dc magnetron sputtering achieved transmittance of more than 80% in the wavelength of 450–700 nm with sheet resistance of less than 10 Ω/◻. An OLED device employing a multilayer transparent electrode consisting of ITO/APC/ITO emitted light with a higher efficacy than that employing a single layer ITO. On the other hand, the multilayer transparent electrode consisting of AZO/APC/AZO did not emit light even though higher corrosion resistance than ITO/APC/ITO was expected.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
73.40.Ns Metal-nonmetal contacts
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Hx Other solid inorganic materials
81.65.Kn Corrosion protection

Recombination probability of oxygen atoms on dynamic stainless steel surfaces in inductively coupled O2 plasmas

Luc Stafford, Joydeep Guha, and Vincent M. Donnelly

J. Vac. Sci. Technol. A 26, 455 (2008); http://dx.doi.org/10.1116/1.2902953 (7 pages) | Cited 6 times

Online Publication Date: 10 April 2008

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The authors have investigated the influence of plasma exposure time (t) on the Langmuir-Hinshelwood (i.e., delayed) recombination of O atoms on electropolished stainless steel surfaces using the spinning-wall method. They found a recombination probability (γO) of 0.13±0.01 after about 60 min of plasma exposure. γO decreased to 0.09±0.01 for t ≥ 12 h and was independent of the O flux impinging onto the surface. These recombination probabilities are much lower than those obtained in plasma chambers exclusively made of stainless steel, but similar to values recorded in stainless steel reactors with large silica surfaces exposed to the plasma. Near real-time elemental analysis by in situ Auger electron spectroscopy showed that the stainless steel surface became rapidly coated with a Si-oxide-based layer (Fe:[Si+Al]:O ≈ 2:1:9 for t = 60 min and 1:2:9 for t = 12 h), due to the slow erosion of the silica discharge tube and anodized Al chamber walls. Thus, the recombination probability of oxygen atoms on stainless steel in plasma reactors with large amounts of exposed silica is largely determined by the amount of sputtered silica coating the chamber walls.
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52.77.-j Plasma applications
81.65.Ps Polishing, grinding, surface finishing
79.20.Fv Electron impact: Auger emission
81.15.Cd Deposition by sputtering

Operational regimes of the saddle field plasma enhanced chemical vapor deposition system

Erik V. Johnson, Stefan Zukotynski, and Nazir P. Kherani

J. Vac. Sci. Technol. A 26, 462 (2008); http://dx.doi.org/10.1116/1.2902958 (10 pages)

Online Publication Date: 21 April 2008

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The electrical potential at the substrate surface during the growth of hydrogenated microcrystalline silicon in a direct current saddle field (SF) plasma enhanced chemical vapor deposition (PECVD) system has been previously shown to be a limiting factor for the formation of the microcrystalline phase in the resulting thin films. The authors examine the extension of this concept to large areas under conditions necessary to obtain microcrystalline silicon in a SF-PECVD system—namely the use of hydrogen-diluted silane as a source gas, pressures between 100 and 300 mTorr, and substrate electrical bias between 100 and 250 V. The response of the SF-PECVD system to electrical substrate bias under these conditions is examined in detail, and four regimes of operation are identified, only one of which is useful for the growth of this particular material system. The delineation of these regimes provides new constraints and guidelines for the application of SF-PECVD technology to large-area deposition of thin films sensitive to ion bombardment during growth, such as microcrystalline silicon.
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81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
52.77.Dq Plasma-based ion implantation and deposition

Plasma-assisted atomic layer deposition of Ta2O5 from alkylamide precursor and remote O2 plasma

S. B. S. Heil, F. Roozeboom, M. C. M. van de Sanden, and W. M. M. Kessels

J. Vac. Sci. Technol. A 26, 472 (2008); http://dx.doi.org/10.1116/1.2905250 (9 pages) | Cited 9 times

Online Publication Date: 21 April 2008

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Tantalum oxide (Ta2O5) films were synthesized by plasma-assisted atomic layer deposition from pentakis(dimethylamino)tantalum (Ta[N(CH3)2]5), precursor and remote O2 plasma as oxidation source. Film growth was monitored in situ by spectroscopic ellipsometry, and film properties were investigated for deposition temperatures between 100 and 225 °C. Saturated precursor dosing conditions and plasma exposure times were identified and growth rates ranging from 0.8 Å/cycle at 225 °C to 0.87 Å/cycle at 100 °C were obtained. The deposited films were found to be stoichiometric (Ta:O = 2:5). Moreover, no N incorporation was detected, and the C content was below the detection limit of the Rutherford backscattering measurement (<2 at. %) for all films studied. The mass density of the films, ranging from 7.8 g cm−3 at 100 °C to 8.1 g cm−3 at 225 °C, was found to be close to the bulk Ta2O5 density. The deviation could partly be accounted for by the amount of H detected with elastic recoil detection analysis, varying from 2 at. % at 225 °C to 4.6 at. % at 100 °C. X-ray diffraction revealed that all films were amorphous, independent of deposition temperature. The reaction mechanisms, in particular, during the plasma step, were investigated by using quadrupole mass spectrometry and optical emission spectroscopy. During the plasma step, combustion products such as CO, CO2, and H2O were detected. This indicates that combustionlike processes occur, in which the alkylamide N(CH3)2 ligands are oxidized by the O radicals generated in the plasma. Additionally, the presence of excited CN* molecules in the plasma was observed in the plasma emission.
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68.55.at Other materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
52.77.Dq Plasma-based ion implantation and deposition
81.65.Mq Oxidation

Dielectric properties of high-density-plasma fluorinated-silicate glass by doping nitrogen

B. J. Wei, Y. L. Cheng, Y. L. Wang, F. H. Lu, and H. C. Shih

J. Vac. Sci. Technol. A 26, 481 (2008); http://dx.doi.org/10.1116/1.2905251 (4 pages)

Online Publication Date: 23 April 2008

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Nitrogen-doped fluorinated-silicate-glass (N-FSG) films were prepared by adding N2 gas to the SiH4/SiF4/O2/Ar gas mixtures using high-density-plasma (HDP) chemical vapor deposition method. When N2 is increasingly added, the fluorine concentration of the films increases and the dielectric constant decreases from 3.8 to 3.4. In addition, better gap-filling ability is obtained by adding N2 due to a lowered deposition/(sputtering+etching) (D/S+E) ratio. Moreover, these films were stabilized by a decreased change in dielectric constant after thermal treatment; indicating a significant improvement in the thermal resistivity of the films. It is proposed that the improvement of stability is correlated with the reduction of unstable fluorine bonds in the N-FSG films. Furthermore, the thermal stability of the N-FSG films was also identified by Al wiring delamination check. After annealing, the blister was observed only in non-N2 FSG film with 5.5% Si–F concentration, while no blisters or delamination were observed when N2 is introduced into the FSG process. Therefore, the N-FSG film, deposited by HDP-chemical vapor deposition, was a good candidate for the interconnect dielectric application.
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77.22.Ch Permittivity (dielectric function)
61.43.Fs Glasses
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
52.77.-j Plasma applications
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
66.70.Hk Glasses and polymers

Surface phase diagram and alloy formation for antimony on Au(110)

S. S. Parihar and P. F. Lyman

J. Vac. Sci. Technol. A 26, 485 (2008); http://dx.doi.org/10.1116/1.2905249 (9 pages)

Online Publication Date: 25 April 2008

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The authors have evaporated submonolayer to monolayer Sb films on the clean Au(110) surface and investigated the resultant Sb-induced reconstructions using low energy electron diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy, and surface x-ray diffraction. They discovered a sequence of reconstructions, namely, c(2×2), (math×math)R54.7°, (math), and p(5×6), with increasing coverage of Sb. The well-known (2×1) reconstruction of the clean Au(110) surface changes to c(2×2) at an Sb coverage of θ ≈ 0.5 ML. At higher Sb coverages, there is a phase transition from c(2×2) to (math×math)R54.7°, with the (math×math)R54.7° pattern emerging at an Sb coverage of θ ≈ 0.7 ML. Upon further deposition, the superstructure spots of the (math×math)R54.7° reconstruction each split into two, resulting in the (math) pattern at a coverage of θ ≈ 0.8 ML. Finally, an Sb/Au(110)-p(5×6) reconstruction emerges at coverages in excess of 1 ML. They have also studied the temperature dependence of the c(2×2) surface phase.
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68.35.bd Metals and alloys
68.47.De Metallic surfaces
68.35.Rh Phase transitions and critical phenomena
81.30.Bx Phase diagrams of metals, alloys, and oxides
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Evolution of epitaxial Ta2O5 and Ta2O films during thermal oxidation of epitaxial tantalum films on sapphire substrates

S. Gnanarajan and S. K. H. Lam

J. Vac. Sci. Technol. A 26, 494 (2008); http://dx.doi.org/10.1116/1.2909971 (4 pages)

Online Publication Date: 25 April 2008

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The evolution of the tantalum oxide structure during low pressure thermal oxidation of epitaxial Ta films on a sapphire substrate was investigated. Thin Ta films were deposited using magnetron sputtering on sapphire substrates at a temperature of 700 °C. Thermal oxidation of these films in oxygen at a pressure of 1.0 Pa at a temperature of 700 °C produced epitaxial Ta2O and Ta2O5 films as determined by x-ray diffraction techniques. The epitaxial Ta2O film had a cubic structure with a (101) plane oriented in the substrate plane. The epitaxial Ta2O5 films had a twinned orthorhombic structure with a (201) plane oriented in the substrate plane.
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68.55.aj Insulators
81.65.Mq Oxidation

Seasoning of plasma etching reactors: Ion energy distributions to walls and real-time and run-to-run control strategies

Ankur Agarwal and Mark J. Kushner

J. Vac. Sci. Technol. A 26, 498 (2008); http://dx.doi.org/10.1116/1.2909966 (15 pages) | Cited 5 times

Online Publication Date: 25 April 2008

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Wafer-to-wafer process reproducibility during plasma etching often depends on the conditioning of the inside surfaces of the reactor. Passivation of reactor surfaces by plasma generated species, often called seasoning, can change the reactive sticking coefficients of radicals, thereby changing the composition of the radical and ion fluxes to the wafer. Ion bombardment of the walls may influence these processes through activation of surface sites or sputtering, and so the spatial variation of ion energies on the walls is important. These seasoning processes may occur during a single etching process or on a wafer-to-wafer basis. The seasoning of plasma etching reactors will be discussed using results from a computational investigation of p-Si etching in chlorine plasmas. The transport of etch products, passivation of walls, and sputtered products from walls are accounted for, as well as differentiating the ion energy distributions to different surfaces. A real-time, closed-loop control of etch rate to counter the effects of seasoning was achieved using the bias voltage as an actuator.
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52.77.Bn Etching and cleaning
81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning

Compositional analysis of lead telluride films deposited via pulsed electron-beam ablation

A. Steigerwald, R. Aga, W. E. Collins, R. Mu, and A. B. Hmelo

J. Vac. Sci. Technol. A 26, 513 (2008); http://dx.doi.org/10.1116/1.2911631 (4 pages)

Online Publication Date: 25 April 2008

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Pulsed electron deposition (PED) is a novel thin film growth technique with unique advantages for industrial-scale manufacturing. Previously, no investigations into local deviations in stoichiometry have been carried out. The authors report the first analysis of large-scale compositional variations in thin films deposited via PED. Ablated lead telluride (PbTe) was deposited at various target-substrate distances on 5 cm2 substrates. Rutherford backscattering was employed to systematically analyze compositional variation at different positions within the deposition. Stoichiometry is reported as a function of both distance and angular displacement. Deposition rates for the center of the ablated plume are reported. The authors show PED to be capable of uniform deposition over areas of moderate (0.5–1 cm2) size, with an enrichment of heavier elements in the center of the film. The results are explained within the context of expanding plasma behavior.
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81.05.Hd Other semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.ag Semiconductors
61.66.Bi Elemental solids
61.66.Dk Alloys
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Methods of producing plasma enhanced chemical vapor deposition silicon nitride thin films with high compressive and tensile stress

M. Belyansky, M. Chace, O. Gluschenkov, J. Kempisty, N. Klymko, A. Madan, A. Mallikarjunan, S. Molis, P. Ronsheim, Y. Wang, D. Yang, and Y. Li

J. Vac. Sci. Technol. A 26, 517 (2008); http://dx.doi.org/10.1116/1.2906259 (5 pages) | Cited 3 times

Online Publication Date: 29 April 2008

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Various methods of generating high stress in thin plasma enhanced chemical vapor deposition (PECVD) silicon nitride (SiN) films are reported. Besides the mainstream variation of plasma power and other process parameters, novel techniques such as creation of high density layers in multilayer PECVD structures or exposure of SiN films to ultraviolet radiation are shown to increase intrinsic film stress. Thin PECVD SiN films have been analyzed by a variety of analytical techniques including Fourier transform infrared spectroscopy, x-ray reflectivity (XRR), time of flight secondary ion mass spectrometry, and transmission electron microscopy to collect data on bonding, density, chemical composition, and film thickness. The level of bonded hydrogen as well as film density has been found to correlate with film stress. Creation of multilayer structures and high density layers help to build up more stress compared to a standard single layer film deposition. Both the density and number of layers in a film, characterized by XRR, affect the stress. Higher density layers affect diffusion profiles and show impurity oscillations corresponding to a multilayer film structure. Ultraviolet cure allows the film to achieve higher level of tensile stress at relatively low temperatures (400–500 °C), comparable to the result of film high temperature annealing.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.at Other materials
68.55.J- Morphology of films
68.65.Ac Multilayers
68.60.Bs Mechanical and acoustical properties
78.66.Nk Insulators

Multiparameter investigation of the sputtering behavior of Ag/Cu Alloys for low energy argon ion bombardment

K. W. Pierson, C. D. Hawes, J. T. Kollwitz, and A. S. Padrón

J. Vac. Sci. Technol. A 26, 522 (2008); http://dx.doi.org/10.1116/1.2905247 (15 pages)

Online Publication Date: 30 April 2008

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The sputtering behavior of Ag/Cu alloys due to low energy (100–1500 eV) Ar+ bombardment as a function of component composition, sample temperature, ion current density, ion dose, and ion energy has been completed. The results indicate that the surface topography development is a strong function of temperature and depends to a lesser extent on ion energy, ion dose, and ion current density. The surface at low temperature coupled with low ion dose and/or low ion current density is flat and faceted with widely dispersed large cones. As the temperature is raised, the rate of Ag surface diffusion increases faster than that of Cu and Ag begins to coat the Cu grains thereby, decreasing the subsequent erosion of the Cu. Selective sputtering of the higher yield Ag and continuous Ag diffusion toward the surface results in a decrease in the Ag concentration in the near surface region as measured by energy dispersive spectroscopy. Auger electron spectroscopy (AES) depth profiles indicate significant diffusion of both Cu and Ag when the electron beam was used in spot mode. Angular distributions of sputtered material indicate that Ag is ejected more preferentially at large angles to the surface normal. The total sputter yield is a function of temperature, ion energy, and dose. These effects are related to the growth of surface topography and the subsequent recapture of ejected material on to the sides of surface features. A method of increasing the thermal conductivity between the sample and holder using graphite colloid was found to affect the surface topography growth and AES profiles. The results of these experiments have implications for depth profiling of multicomponent metallic alloys.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.bd Metals and alloys
68.35.Fx Diffusion; interface formation
79.20.Fv Electron impact: Auger emission
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

Finite element modeling and experimental validation of the sealing mechanism of the ConFlat® joint

P. Lutkiewicz and Ch. Rathjen

J. Vac. Sci. Technol. A 26, 537 (2008); http://dx.doi.org/10.1116/1.2906258 (8 pages) | Cited 2 times

Online Publication Date: 30 April 2008

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The sealing mechanism of flat copper gaskets and ConFlat (CF) flanges is studied. Finite element (FE) modeling was used and the results were validated through experiments. Only a part of the CF flange knife surface contributes to the sealing. A bilinear character of compression force and displacement evolution was numerically and experimentally identified and has been described by a phenomenological formula. The influence of the flange collar and gasket material properties on the sealing mechanism was studied. The plastic strain field produced by the knife in the gasket was compared to microhardness tests. The possibility of crack propagation was studied because of large plastic deformation (FE results) near the knife tip.
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89.20.Kk Engineering
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Role of chamber dimension in fluorocarbon based deposition and etching of SiO2 and its effects on gas and surface-phase chemistry

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

J. Vac. Sci. Technol. A 26, 545 (2008); http://dx.doi.org/10.1116/1.2909963 (10 pages) | Cited 3 times

Online Publication Date: 30 April 2008

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It is well understood that chamber geometry is an influential factor governing plasma processing of materials. Simple models suggest that a large fraction of this influence is due to changes in basic plasma properties, namely, density, temperature, and potential. However, while such factors do play an important role, they only partly describe the observed differences in process results. Therefore, to better elucidate the role of chamber geometry in this work, the authors explore the influence of plasma chemistry and its symbiotic effect on plasma processing by decoupling the plasma density, temperature, and potential from the plasma-surface (wall) interactions. Specifically, a plasma system is used with which the authors can vary the chamber dimension so as to vary the plasma-surface interaction directly. By varying chamber wall diameter, 20–66 cm, and source-platen distance, 4–6 cm, the etch behavior of SiO2 (or the deposition behavior of fluorocarbon polymer) and the resulting gas-phase chemistry change significantly. Results from in situ spectroscopic ellipsometry show significant differences in etch characteristics, with etch rates as high as 350 nm/min and as low as 75 nm/min for the same self-bias voltage. Fluorocarbon deposition rates are also highly dependent on chamber dimension and vary from no net deposition to deposition rates as high as 225 nm/min. Etch yields, however, remain unaffected by the chamber size variations. From Langmuir probe measurements, it is clear that chamber geometry results in significant shifts in plasma properties such as electron and ion densities. Indeed, such measurements show that on-wafer processes are limited at least in part by ion flux for high energy reactive ion etch. However, in situ multipass Fourier transform infrared spectroscopy reveals that the line-averaged COF2, SiF4, CF2, and CF3 gas-phase densities are also dependent on chamber dimension at high self-bias voltage and also correlate well to the CFx overlayer stoichiometry under deposition conditions.
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52.77.Dq Plasma-based ion implantation and deposition
52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties
52.40.Hf Plasma-material interactions; boundary layer effects
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