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Mar 2009

Volume 27, Issue 2, pp. L1-415

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Chemical and structural properties of atomic layer deposited La2O3 films capped with a thin Al2O3 layer

X. L. Li, D. Tsoutsou, G. Scarel, C. Wiemer, S. C. Capelli, S. N. Volkos, L. Lamagna, and M. Fanciulli

J. Vac. Sci. Technol. A 27, L1 (2009); http://dx.doi.org/10.1116/1.3079632 (7 pages) | Cited 5 times

Online Publication Date: 27 February 2009

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X-ray diffraction and infrared spectroscopy measurements are conducted in order to assess the crystallographic structure and chemical purity of lanthanum oxide (La2O3) films grown by atomic layer deposition (ALD) on Si substrates. In situ capping with thin aluminum oxide (Al2O3) layer is proved to be beneficial in preventing the formation of lanthanum hydroxide phases. The effect of two process parameters, namely, La2O3 film growth temperature (260–500 °C range) and postdeposition annealing temperature (600–1100 °C range), on the chemical and structural evolutions of Al2O3/La2O3/Si stacks is discussed. This study enables the identification of the optimum ALD growth recipe yielding the highest hexagonal La2O3 phase content, which might be suitable for integration into innovative metal oxide semiconductor devices.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.30.Hv Other nonmetallic inorganics
78.66.Db Elemental semiconductors and insulators
68.55.aj Insulators
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Relatively low temperature synthesis of hexagonal tungsten carbide films by N doping and its effect on the preferred orientation, phase transition, and mechanical properties

Y. D. Su, C. Q. Hu, C. Wang, M. Wen, and W. T. Zheng

J. Vac. Sci. Technol. A 27, 167 (2009); http://dx.doi.org/10.1116/1.3058721 (7 pages) | Cited 2 times

Online Publication Date: 6 February 2009

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The authors deposited N-doped tungsten carbide thin films on Si(100) substrates at 500 °C using direct-current reactive magnetron sputtering in a mixture of CH4/N2/Ar discharge and explored the effects of N doping on the preferred orientation, phase transition, and mechanical properties of the films by using x-ray diffraction, x-ray photoelectron spectroscopy, and nanoindentation measurements. They found that N doping significantly influenced the compressive stress, which led to a pronounced change in the preferred orientation, phase structure, and hardness for the tungsten carbide film. A phase transition from β-WC to α-WC occurred when N doping was in the range of 2.9 and 4.7 at. %, meaning that α-WC can be obtained at relatively low temperature (500 °C). To reveal the relationship between the stress and phase transition, as well as preferred orientation, the density-functional theory based on first principles was used to calculate the elastic constants and shear modulus for tungsten carbide with a structure of β-WC or α-WC. The calculated results showed that the preferred orientation depended on the competition between strain energy and surface energy, as well as the grains competitive growth, and the phase transition can be attributed to a decrease in the strain energy. The hardness of α-WC was harder than β-WC because the shear modulus for α-WC was larger than that of β-WC, whereas the bulk modulus for α-WC was almost equal to that of β-WC.
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68.60.Bs Mechanical and acoustical properties
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
81.40.Lm Deformation, plasticity, and creep
62.20.de Elastic moduli
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Influence of the bias voltage on the structure and mechanical performance of nanoscale multilayer CrAlYN/CrN physical vapor deposition coatings

G. Sáfrán, C. Reinhard, A. P. Ehiasarian, P. B. Barna, L. Székely, O. Geszti, and P. Eh. Hovsepian

J. Vac. Sci. Technol. A 27, 174 (2009); http://dx.doi.org/10.1116/1.3065675 (9 pages) | Cited 1 time

Online Publication Date: 6 February 2009

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The effects of bias voltage on the microstructure and the related tribological properties of CrAlYN/CrN nanoscale multilayer superlattice coatings were investigated. The coatings were deposited at 450 °C substrate temperature by combined high power impulse magnetron sputtering (HIPIMS) and unbalanced magnetron sputtering techniques. The substrates were 304 stainless steel, M2 high speed steel for structural analysis and mechanical testing, as well as cemented carbide substrates end mills for dry high speed milling applications. Substrates were pretreated by HIPIMS etching. The bias voltage Ub was varied between −75 and −150 V. The chemical composition was determined by neutral mass spectroscopy. The microstructure was characterized by x-ray diffraction and cross sectional transmission electron microscopy. All coatings had a single phase B1 fcc structure. The chemical composition was not affected by the bias voltage. Local epitaxial or axiotaxial growth attributed to the HIPIMS etching pretreatment was observed on the large surface areas of the substrate crystals. This turned to columnar growth with {110} texture at low bias voltages Ub between −75 and −120 V, while at Ub = −150 V an equiaxed structure of large crystal sizes developed with {111} texture. At the same time the waviness of the superlattice significantly decreased. An increase in bias voltage resulted in a significant rise in both residual stress levels (from −3.3 to −9.5 GPa) and plastic hardness (from Hp = 34–51 GPa), while the coating/substrate adhesion decreased from 61 to 45 N. The friction coefficient increased from 0.43 (at Ub = −75 V) to 0.55 (at UB = −120 V), while the initial sliding wear rates decreased remarkably (2.6×10−16 m3 N−1 m−1 at UB = −75 V to 3.7×10−17 m3 N−1 m−1 at Ub = −150 V). The life time of 8 mm ball-nosed cemented carbide end mills decreased from 39 min at Ub = −75 V to 19 min when Ub was raised to −150 V. These results highlight that the combination of HIPIMS substrate treatment and designed deposition parameters provides good opportunity to tailor coating structures with optimized properties.
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62.25.-g Mechanical properties of nanoscale systems
68.35.Gy Mechanical properties; surface strains
62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
68.65.Ac Multilayers
68.65.Cd Superlattices

Thermal-mechanical modeling of nodular defect embedded within multilayer coatings

Xiulan Ling, Jianda Shao, and Zhengxiu Fan

J. Vac. Sci. Technol. A 27, 183 (2009); http://dx.doi.org/10.1116/1.3065676 (4 pages) | Cited 1 time

Online Publication Date: 6 February 2009

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The initiation of laser damage within optical coatings can be better understood by thermal-mechanical modeling of coating defects. The result of this modeling shows that a high-temperature rise and thermal stress can be seen just inside the nodular defect compared to surrounding coating layers. The temperature rise and thermal stress tend to increase with seed diameter. Shallower seed tend to cause higher temperature rise and greater thermal stress. There is a critical seed depth at which thermal stress is largest. The composition of the seed resulting from different coating-material emission during evaporation can affect the temperature rise and thermal stress distribution.
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81.40.Gh Other heat and thermomechanical treatments
42.79.Wc Optical coatings
68.60.Bs Mechanical and acoustical properties
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
77.55.-g Dielectric thin films

Photon emission during fracture of carbon materials

K. Yasuda, K. Yamamoto, T. Shiota, and Y. Matsuo

J. Vac. Sci. Technol. A 27, 187 (2009); http://dx.doi.org/10.1116/1.3065677 (6 pages)

Online Publication Date: 6 February 2009

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Photon emission (phE) during fracture was investigated on glass-like carbon, pyrolytic graphite, polycrystalline graphite, and carbon fiber reinforced composites (C/C composites). The C/C composites were heat treated at 1000, 1500, and 2000 °C. The specimen was fractured by three-point bending and the resulting phE was measured at atmospheric pressure, 10−3 and 10−6 Pa. The phE was not observed on any samples at atmospheric pressure, whereas it occurred on the glass-like carbon and C/C composites at 10−3 and 10−6 Pa. The phE intensity at 10−3 Pa was higher than that at 10−6 Pa. This study revealed that the phE on the carbon materials depended on their crystal structure and surrounding gas pressure. The gas pressure dependence suggests that the phE resulted from gas discharge.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mm Fracture
81.40.Gh Other heat and thermomechanical treatments
79.60.-i Photoemission and photoelectron spectra

Chemistry in long residence time fluorocarbon plasmas

S. P. Sant, C. T. Nelson, L. J. Overzet, and M. J. Goeckner

J. Vac. Sci. Technol. A 27, 193 (2009); http://dx.doi.org/10.1116/1.3065678 (16 pages) | Cited 3 times

Online Publication Date: 6 February 2009

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The densities of radicals and neutrals in fluorocarbon (FC) plasmas have been investigated in an inductively coupled plasma system to understand the predominant gain and loss mechanisms of dissociative products and their interaction with chamber surfaces. The input parameters varied in this experiment are the source to chuck gap and the F: C ratio of the feed gas. The densities of F, CF2, CF3, CF4, C2F4, SiF4, COF2, CO, and CO2 are measured and analyzed. In addition, two different forms of C4F8, the standard cyclic c and a radical linear l structures are observed in C4F8 containing plasmas. l-C4F8 is shown to be the primary dissociation product of c-C4F8 and, thus, cannot be neglected from calculations of the loss rate of c-C4F8 to electron collisions. This implies that the typically cited dissociative products of c-C4F8 (primarily C2F4) can have dual production channels: one from l-C4F8 and the other directly from c-C4F8. Furthermore, the measured density of CF4 shows strong correlation to the loss of F to the surfaces, indicating its primary production mechanism is from surface recombination. Similarly, CF3 is mainly produced from deposited FC film on chamber surfaces and lost to electron impact reactions. The etch products resulting from etch of the quartz window are shown, and an overall neutral density model is developed.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
52.25.-b Plasma properties
52.40.Hf Plasma-material interactions; boundary layer effects

Plasma etching of Hf-based high-k thin films. Part I. Effect of complex ions and radicals on the surface reactions

Ryan M. Martin and Jane P. Chang

J. Vac. Sci. Technol. A 27, 209 (2009); http://dx.doi.org/10.1116/1.3065679 (8 pages) | Cited 3 times

Online Publication Date: 6 February 2009

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The effect of ion and radical compositions in BCl3/Cl2 plasmas was assessed in this work with a focus on the formation of etch products in patterning hafnium aluminate, a potential high-k gate oxide material. The plasma composition became increasingly more complex as the percentage of boron trichloride was increased, which led to the formation of a significant amount of boron-containing species including B+, BCl+, BCl2+, BCl3+, B2Cl3+, and B2OCl3+ in the plasma. The BCl2+ ions were found to be the dominant species in BCl3 containing plasmas at most conditions; however, increasing the pressure or decreasing the power led to an increase in the formation of higher mass ions. Several compositions of Hf1−xAlxOy thin films ranging from pure HfO2 to pure Al2O3 were etched in BCl3/Cl2 plasmas as functions of ion energy and plasma composition. The etch product distributions were measured and the dominant metal-containing etch products were HfClx and AlClx in a Cl2 plasma and HfClx, HfBOCl4, and AlxCly in a BCl3 plasma, and their concentrations increased with increasing ion energy. Oxygen was detected removed in the form of ClO in Cl2 and as trichloroboroxin ((BOCl)3) in BCl3. Both the etch rate and the etch product formation are enhanced in BCl3/Cl2 plasmas, as compared to those in Cl2 plasmas, due to the change in the composition and reactivity of the dominant ions and radicals.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Plasma etching of Hf-based high-k thin films. Part II. Ion-enhanced surface reaction mechanisms

Ryan M. Martin, Hans-Olof Blom, and Jane P. Chang

J. Vac. Sci. Technol. A 27, 217 (2009); http://dx.doi.org/10.1116/1.3065695 (7 pages) | Cited 3 times

Online Publication Date: 6 February 2009

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The mechanism for ion-enhanced chemical etching of hafnium aluminate thin films in Cl2/BCl3 plasmas was investigated in this work, specifically how the film composition, ion energy, and plasma chemistry determine their etch rates. Several compositions of Hf1−xAlxOy thin films ranging from pure HfO2 to pure Al2O3 were etched in BCl3/Cl2 plasmas and their etch rates were found to scale with math in both Cl2 and BCl3 plasmas. In Cl2 plasmas, a transition point was observed around 50 eV, where the etch rate was significantly enhanced while the linear dependence to math was maintained, corresponding to a change in the removal of fully chlorinated to less chlorinated reaction products. In BCl3 plasma, deposition dominates at ion energies below 50 eV, while etching occurs above that energy with an etch rate of three to seven times that in Cl2. The faster etch rate in BCl3 was attributed to a change in the dominant ion from Cl2+ in Cl2 plasma to BCl2+ in BCl3, which facilitated the formation of more volatile etch products and their removal. The surface chlorination (0–3 at. %) was enhanced with increasing ion energy while the amount of boron on the surface increases with decreasing ion energy, highlighting the effect of different plasma chemistries on the etch rates, etch product formation, and surface termination.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
77.55.-g Dielectric thin films

Plasma etching of Hf-based high-k thin films. Part III. Modeling the reaction mechanisms

Ryan M. Martin and Jane P. Chang

J. Vac. Sci. Technol. A 27, 224 (2009); http://dx.doi.org/10.1116/1.3065705 (6 pages) | Cited 2 times

Online Publication Date: 6 February 2009

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A generalized etch rate model was formulated to describe metal oxide etching in complex plasma chemistries, based on the understanding gained from detailed plasma characterization and experimental investigation into the metal oxide etching mechanisms. Using a surface site balance-based approach, the correct etch rate dependencies on neutral-to-ion flux ratio, ion energy, competing deposition and etching reaction pathways, and film properties were successfully incorporated into the model. The applicability of the model was assessed by fitting to experimental etch rate data in both Cl2 and BCl3 chemistries. Plasma gas phase analysis as well as etch and deposition rate measurements were used to calculate initial values and appropriate ranges for model parameter variation. Physically meaningful parameter values were extracted from the modeling fitting to the experimental data, thereby demonstrating the applicability of this model in assessing the plasma etching of other complex materials systems.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
77.55.-g Dielectric thin films

Growth modes in metal-organic molecular beam epitaxy of TiO2 on r-plane sapphire

Bharat Jalan, Roman Engel-Herbert, Joël Cagnon, and Susanne Stemmer

J. Vac. Sci. Technol. A 27, 230 (2009); http://dx.doi.org/10.1116/1.3065713 (4 pages) | Cited 8 times

Online Publication Date: 6 February 2009

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Phase pure, epitaxial (101) rutile TiO2 films were grown on (012) sapphire substrates at temperatures between 485 and 725 °C using metal-organic molecular beam epitaxy with titanium tetraisopropoxide as the Ti source. Growth modes and rates were investigated as a function of substrate temperature using reflection high-energy electron diffraction, x-ray reflectivity, atomic force microscopy, and transmission electron microscopy. Growth rates were as high as 125 nm/h. The influence of additional oxygen supplied from a rf plasma source was investigated. Without oxygen plasma, the growth rate exhibited reaction and flux-limited regimes and layer-by-layer growth was observed in the initial stages of film growth. With oxygen plasma the growth rate became independent of temperature; films grew initially in step-flow mode and were insulating. The mechanisms for the different growth modes as a function of film thickness, temperature, and presence of oxygen are discussed.
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68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.-j Plasma applications

Correlation of chemical composition and electrical properties of rf sputtered alumina films

M. Voigt, A. Bergmaier, G. Dollinger, and M. Sokolowski

J. Vac. Sci. Technol. A 27, 234 (2009); http://dx.doi.org/10.1116/1.3065978 (11 pages) | Cited 3 times

Online Publication Date: 6 February 2009

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Alumina films were prepared by radio frequency magnetron sputtering from an aluminum oxide target on an indium tin oxide covered glass. The purpose of the study was to test the influence of the sputter parameters on the elemental composition, surface morphology, and electrical insulation properties (breakdown fields and leakage currents). Tested parameters were the sputter gas (Ar) pressure, the sputter rate, the sputter power, the sputter gas composition (Ar:O2), the conditioning of the target, the residual base pressure, and the substrate temperature. The surface morphology of the films was investigated by atomic force microscopy. Depth profiles of the elemental compositions were measured by elastic recoil detection using energetic heavy ions, and the insulation properties were investigated by current voltage measurements and impedance spectroscopy. The main finding is that the leakage currents increase by about five orders of magnitude, if the atomic ratio of O:Al increases from 1.35 to 2.0. In parallel the breakdown fields decrease by a factor of 100, and the character of the breakdowns changes from soft to hard. The highest breakdown fields (2.4 MV/cm) and smallest leakage currents (6.5×10−8 A/cm2 at 2.0 MV/cm) are obtained for slightly Al rich films with small atomic concentrations of H (<0.5 at. %). These films were sputtered in pure Ar and under the lowest possible pressure of the residual gas.
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77.22.Jp Dielectric breakdown and space-charge effects
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
81.15.Cd Deposition by sputtering
73.61.Ng Insulators
82.80.Fk Electrochemical methods

Energy scaling of the ion-induced desorption yield for perpendicular collisions of Ar and U with stainless steel in the energy range of 5 and 100 MeV/u

H. Kollmus, A. Krämer, M. Bender, M. C. Bellachioma, H. Reich-Sprenger, E. Mahner, E. Hedlund, L. Westerberg, O. B. Malyshev, M. Leandersson, and E. Edqvist

J. Vac. Sci. Technol. A 27, 245 (2009); http://dx.doi.org/10.1116/1.3065979 (3 pages) | Cited 1 time

Online Publication Date: 12 February 2009

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For the GSI future project Facility for Antiproton and Ion Research a beam intensity of 1012 U28+ions/s is planned to be extracted from the GSI heavy ion synchrotron SIS18. Measurements performed in 2001 showed that the beam lifetime of the ions in the synchrotron is decreasing with increasing number of injected particles due to vacuum instabilities caused by ion-induced desorption. The injection energy for the SIS18 is about 10 MeV/u and U28+ ions are accelerated to 200 MeV/u limited by the magnetic rigidity for the low charge state. The aim of this work was to measure the desorption yield as a function of the impact energy from injection to extraction of SIS18 at GSI. Low energy yields at 5.0, 9.7, and 17.7 MeV/u were measured at the Cyclotron of The Svedberg Laboratory in Uppsala. High energy yields at 40, 80, and 100 MeV/u were measured at SIS18 of GSI in a different setup. It was found that the desorption yield scales with the electronic energy loss (dE/dx)eln, with n between 2 and 3, decreasing for increasing impact energy above the Bragg maximum.
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68.43.Nr Desorption kinetics
68.43.Mn Adsorption kinetics
79.20.Uv Electron energy loss spectroscopy
29.20.dk Synchrotrons
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
29.27.Ac Beam injection and extraction
29.27.Bd Beam dynamics; collective effects and instabilities

Reaction of a hydrogen-terminated Si(100) surface in UHV with ion-pump generated radicals

Janik Zikovsky, Stanislav A. Dogel, Adam J. Dickie, Jason L. Pitters, and Robert A. Wolkow

J. Vac. Sci. Technol. A 27, 248 (2009); http://dx.doi.org/10.1116/1.3071944 (5 pages)

Online Publication Date: 12 February 2009

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The authors present scanning tunneling microscopy images and mass spectra that show that dosing gases at pressures in the range of 10−6 Torr in an ion-pumped ultrahigh vacuum (UHV) chamber results in a measurable concentration of reactive molecular radicals and atomic hydrogen ions being created. One source of radicals is the fragmentation of the dosed molecule, while another is atomic hydrogen that is re-emitted from the ion pump itself. The dosing of noble gases such as helium also results in harmful radicals escaping the ion pump. These radicals are able to create new reactive sites on a hydrogen-terminated Si(100) surface; they show that these new dangling bonds result in extra molecular line growth in a 2,3-dimethyl-1,3-butadiene dosing experiment. These results serve as a cautionary note to experimenters working with ion-pumped UHV systems and surfaces that are sensitive to radicals, such as hydrogen-terminated Si.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Practical expressions for the mean escape depth, the information depth, and the effective attenuation length in Auger-electron spectroscopy and x-ray photoelectron spectroscopy

A. Jablonski and C. J. Powell

J. Vac. Sci. Technol. A 27, 253 (2009); http://dx.doi.org/10.1116/1.3071947 (9 pages) | Cited 12 times

Online Publication Date: 12 February 2009

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The authors report new calculations of mean escape depths (MEDs), information depths (IDs), and effective attenuation lengths (EALs) for 16 photoelectron lines and 9 Auger-electron lines of five elemental solids (Si, Cu, Ag, W, and Au) and four inorganic compounds (ZrO2, ZrSiO4, HfO2, and HfSiO4). These calculations were made to update similar previous calculations with improved data for the transport mean free path (TMFP) that are now available. Ratios of averages of the new MEDs, IDs, and EALs to the inelastic mean free path for electron emission angles between 0° and 50° varied linearly with the single-scattering albedo, a simple function of the inelastic mean free path and TMFP. The slopes of the linear relations depend only weakly on the atomic potential used in calculations of differential elastic-scattering cross sections (from which TMFPs are derived). The new linear relations are simple practical expressions for determining the MED, ID, and EAL for any solid in conventional Auger electron spectroscopy and x-ray photoelectron spectroscopy.
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79.60.-i Photoemission and photoelectron spectra
79.20.Fv Electron impact: Auger emission

Investigation of InP etching mechanisms in a Cl2/H2 inductively coupled plasma by optical emission spectroscopy

L. Gatilova, S. Bouchoule, S. Guilet, and P. Chabert

J. Vac. Sci. Technol. A 27, 262 (2009); http://dx.doi.org/10.1116/1.3071950 (14 pages) | Cited 10 times

Online Publication Date: 12 February 2009

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Optical emission spectroscopy (OES) has been used in order to investigate the InP etching mechanisms in a Cl2–H2 inductively coupled plasma. The authors have previously shown that anisotropic etching of InP could be achieved for a H2 percentage in the 35%–45% range where the InP etch rate also presents a local maximum [ J. Vac. Sci. Technol. B 24, 2381 (2006) ], and that anisotropic etching was due to an enhanced passivation of the etched sidewalls by a silicon oxide layer [ J. Vac. Sci. Technol. B 26, 666 (2008) ]. In this work, it is shown that this etching behavior is related to a maximum in the H atom concentration in the plasma. The possible enhancement of the sidewall passivation process in the presence of H is investigated by comparing OES measurements and etching results obtained for Cl2–H2 and Cl2–Ar gas mixtures.
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81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
52.77.Bn Etching and cleaning

Influence of vacuum annealing on the physical properties of ZnO/Al/ZnO multilayer coatings

M. A. Al-Maghrabi, M. F. Al-Kuhaili, S. M. A. Durrani, and I. A. Bakhtiari

J. Vac. Sci. Technol. A 27, 276 (2009); http://dx.doi.org/10.1116/1.3072512 (6 pages) | Cited 3 times

Online Publication Date: 12 February 2009

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Multilayer ZnO/Al/ZnO coatings were deposited by thermal evaporation on substrates heated to 300 °C. Subsequently, the coatings were annealed in vacuum in the temperature range of 300–600 °C. The structural properties of the films were investigated using x-ray diffraction and atomic force microscopy. The chemical properties were determined from x-ray photoelectron spectroscopy. The electrical and optical properties of the coatings were studied in order to evaluate their performance as transparent conducting coatings. The best performance was obtained with films annealed at 500 °C, for which the average visible transmittance was about 60% and the resistivity was 6.1×10−3 Ω cm.
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61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
68.65.Ac Multilayers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.40.Ns Metal-nonmetal contacts
79.60.-i Photoemission and photoelectron spectra
78.66.-w Optical properties of specific thin films

Effect of pulse frequency on the ion fluxes during pulsed dc magnetron sputtering

M. Rahamathunnisa and D. C. Cameron

J. Vac. Sci. Technol. A 27, 282 (2009); http://dx.doi.org/10.1116/1.3072513 (5 pages) | Cited 1 time

Online Publication Date: 12 February 2009

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The ion fluxes and energies which impinge on the substrate during the deposition of chromium nitride by asymmetric bipolar pulsed dc reactive magnetron sputtering have been analyzed using energy resolved mass spectrometry. It has been found that there is a remarkable increase in ion flux at higher pulse frequencies and that the peak ion energy is directly related to the positive voltage overshoot of the target voltage. The magnitude of the metal flux depositing on the substrate is consistent with a “dead time” of ∼ 0.7 μs at the start of the on period. The variation of the ion flux with pulse frequency has been explained by a simple model in which the ion density during the on period has a large peak which is slightly delayed from the large negative voltage overshoot which occurs at the start of the on pulse due to increased ionization at that time. This is consistent with the previously observed phenomena in pulsed sputtering.
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81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth

Test particle simulation of the role of ballistic electrons in hybrid dc/rf capacitively coupled CF4 plasmas

P. L. G. Ventzek and K. Denpoh

J. Vac. Sci. Technol. A 27, 287 (2009); http://dx.doi.org/10.1116/1.3072922 (8 pages) | Cited 7 times

Online Publication Date: 12 February 2009

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Hybrid dc/rf plasma sources are an emerging equipment technology in plasma etching for semiconductor manufacturing. In this type of plasma source, ballistic electrons originate as secondary electrons on a dc/rf (i.e., VHF, 60 MHz) biased electrode and are then accelerated in the sheath toward an opposite non-dc biased lower electrode. For electropositive (argon) plasmas it has been shown that the primary contribution of ballistic electrons is ionization in the dc sheath and modulation of the discharge properties. Whether applied dc power net increases or decreases the plasma electron density depends on the rf power environment of the opposing substrate electrode. When rf power is applied to a substrate electrode, the rf self-bias creates a potential well that traps the ballistic electrons, the result being that the electron density increases with dc power. In most cases the fraction of high energy electrons that reach the electrode is small. In this article, the authors describe the use of test particle Monte Carlo simulations to describe the behavior of hybrid dc/rf electronegative (CF4) plasmas. In contrast to the behavior in argon, process experiments with electronegative gases such as CF4 indicate that the electron density is independent of dc bias power when no rf power is applied to the wafer. Test particle simulations show that CF4 provides for a “self-confinement” effect caused by large cross sections for vibrational excitation at intermediate to low electron energies, which results in weak dependence of electron density on dc bias voltage when low frequency bias is not applied to the wafer. This emphasizes the important role of gas composition and cross-section structure in the control of dc/rf plasmas. Consistent with experiment, test particle Monte Carlo simulations also show that when rf is applied to the substrate, overall the CF4 plasma’s macroscopic properties are similar manner to argon plasmas. Even so, differences between the argon and CF4 plasmas occur related to the scaling of the fraction of ballistic electrons that reach the wafer as a function of dc and rf power. A regime is identified in which CF4 and argon plasmas have the equivalent ratio of ballistic to thermal electron density adjacent to the surface. The authors explain that the differences are related to different thermalization and ionization mechanisms in these plasmas. In addition, they find the electron attachment constant is zero in the dc sheath and nearly constant value in the bulk as the transit time in the sheath is far less than the mean attachment time. The same simple function to express ionization rate constant as a function of electric field in the dc sheath, developed for argon, can be also applied to CF4.
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52.25.Fi Transport properties
52.65.Pp Monte Carlo methods
52.25.Jm Ionization of plasmas
52.40.Kh Plasma sheaths
52.77.Bn Etching and cleaning
52.50.Dg Plasma sources

Elimination of pillar associated with micropipe of SiC in high-rate inductively coupled plasma etching

Naoya Okamoto

J. Vac. Sci. Technol. A 27, 295 (2009); http://dx.doi.org/10.1116/1.3077297 (6 pages) | Cited 2 times

Online Publication Date: 12 February 2009

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Pillar formation in SiC via holes fabricated by inductively coupled plasma etching at a high etch rate in the order of around 2 μm/min using SF6/O2 was studied by comparing samples etched under different thermal conductivity conditions from wafer to carrier. As a result, it was found that the formation of pillars is attributed to a process in which the origin of micropipes acts as a micromask and is passivated with nonvolatile and difficult-to-etch products of NiSiF, which are generated by a chemical combination of the etched Ni from the metal mask and the formed SiFX species during etching. Furthermore, the optimization of etching conditions to eliminate the pillars in SiC via holes with minimal microtrenches was accomplished at a high etch rate of 2 μm/min and high selectivity over 100 for Ni.
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81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
85.40.Hp Lithography, masks and pattern transfer
66.70.Df Metals, alloys, and semiconductors

High etching rates of bulk Nb in Ar/Cl2 microwave discharge

M. Rašković, S. Popović, J. Upadhyay, L. Vušković, L. Phillips, and A.-M. Valente-Feliciano

J. Vac. Sci. Technol. A 27, 301 (2009); http://dx.doi.org/10.1116/1.3077298 (5 pages) | Cited 2 times

Online Publication Date: 12 February 2009

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Plasma-based Nb surface treatment provides an excellent opportunity to eliminate surface imperfections and increase the cavity quality factor in important applications such as particle accelerators and cavity quantum electrodynamics, as well as Josephson junctions. In this study, plasma etching of bulk Nb is performed on the surface of disk-shaped samples with the goal of eliminating nonsuperconductive pollutants in the penetration depth region and the mechanically damaged surface layer. The authors have demonstrated that in the microwave glow discharge, an etching rate of 1.5 μm/min can be achieved using Cl2 as a reactive gas. The influence of plasma parameters such as input power, pressure, and concentration of the reactive gas on the etching rate is determined. Simultaneously, plasma emission spectroscopy was used to estimate the densities of Cl, Cl+, and Cl2 under various plasma conditions.
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81.65.Cf Surface cleaning, etching, patterning
52.80.Pi High-frequency and RF discharges
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
52.77.Bn Etching and cleaning
74.25.Ha Magnetic properties including vortex structures and related phenomena
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Hydrogen mediated transport of Sn to Ru film surface

Nadir Faradzhev and Vadim Sidorkin

J. Vac. Sci. Technol. A 27, 306 (2009); http://dx.doi.org/10.1116/1.3081968 (9 pages) | Cited 5 times

Online Publication Date: 19 February 2009

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The authors report on the interaction of atomic hydrogen with Sn and thin Ru film at room temperature. The study is done using a combination of photoelectron and low energy ion scattering spectroscopies as well as scanning electron microscopy. The adsorption of hydrogen on a Sn surface leads to the formation of stannane (SnH4), which dissociatively adsorbs on the surface of polycrystalline Ru film. In the range of effective Sn coverages studied (up to 1 ML), the resulting overlayer consists of randomly distributed three-dimensional islands with average size below 40 nm occupying up to several percent of the surface area. Nucleation of Sn is observed presumably at defect sites (e.g., grain boundaries). Ion scattering data are found consistent with Volmer–Weber growth mode: no initial transition wetting layer formation is detected. Oxidation of Sn islands on a Ru surface at room temperature results in the formation of SnO. Neither metallic nor oxidation states of Sn higher than Sn2+ are observed by photoelectron spectroscopy.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
79.60.-i Photoemission and photoelectron spectra
61.72.Mm Grain and twin boundaries
81.65.Mq Oxidation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

A molecular basis for the onset of turbulence

A. Muriel

J. Vac. Sci. Technol. A 27, 315 (2009); http://dx.doi.org/10.1116/1.3079631 (6 pages) | Cited 2 times

Online Publication Date: 20 February 2009

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The authors review the atomic and molecular data to analyze flow experiments on the onset of turbulent flow in gases. They use published and unpublished data from pipe flow experiments and calculate ratios of critical velocities obtained from identical apparatus. In contrast to the use of derived quantities for characterizing the onset of turbulence, such as the Reynolds number, we restrict our data and analysis using observable quantities such as molecular properties and critical velocities. We find a rationale for a molecular origin of turbulence, in contrast to the exclusive use of continuum theory. Several new predictions are made from the molecular theory of turbulence.
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47.27.Cn Transition to turbulence
47.10.ad Navier-Stokes equations
47.60.Dx Flows in ducts and channels

Activation and measurement of nonevaporable getter films

O. B. Malyshev, K. J. Middleman, J. S. Colligon, and R. Valizadeh

J. Vac. Sci. Technol. A 27, 321 (2009); http://dx.doi.org/10.1116/1.3081969 (7 pages) | Cited 7 times

Online Publication Date: 24 February 2009

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An experimental setup for studying the pumping and capacity properties of nonevaporable getter (NEG)-coated films has been designed and built in the ASTeC Vacuum Science Laboratory at Daresbury Laboratory. The measurement system is based on the dynamic expansion method with a gas injection system that is capable of injecting the residual gases present in a typical UHV system, such as H2, CO, CO2, and CH4. The test particle Monte Carlo model was used for accurate evaluation of NEG film sticking probability from the pressure reading during gas injection. The experimental measurements with NEG-coated samples have shown that the NEG film can be poisoned during the NEG film activation (and/or regeneration) by molecules of CO and CO2 desorbed from uncoated parts of the vacuum chamber. The effect of NEG film poisoning was reduced by lowering the temperature of the uncoated parts of the vacuum chamber during the NEG film activation and, as a result, a new activation procedure was developed for vacuum systems containing NEG-coated parts.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Yx Interaction between different crystal defects; gettering effect
68.43.Nr Desorption kinetics

Surface chemistry and surface electronic properties of ZnO single crystals and nanorods

J. J. Uhlrich, D. C. Olson, J. W. P. Hsu, and T. F. Kuech

J. Vac. Sci. Technol. A 27, 328 (2009); http://dx.doi.org/10.1116/1.3085723 (8 pages) | Cited 6 times

Online Publication Date: 25 February 2009

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The surface chemistry of ZnO single crystals of (0001) and (10math0) orientations and ZnO nanorods was studied using x-ray and ultraviolet photoelectron spectroscopies. Air drying and UV-ozone preparations were studied in particular as chemical treatments that could be applied to poly(3-hexylthiophene) (P3HT)-ZnO solar cells to enhance performance. The UV-ozone treatment showed negligible effect by photoelectron spectroscopy on the ZnO single crystal surfaces, but brought about electronic shifts consistent with increased upward band bending by ∼ 0.25 eV on the ZnO nanorod surface. Modest interface dipoles of ∼ 0.15 and ∼ 0.25 eV were measured between P3HT and the (10math0) and (0001) single crystal orientations, respectively, with the dipole moment pointing from ZnO to the P3HT layer. The sol-gel films showed evidence of forming a small interface dipole in the opposite direction, which illustrates the difference in surface chemistry between the solution-grown ZnO and the ZnO single crystals.
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81.07.Bc Nanocrystalline materials
73.61.Ga II-VI semiconductors
73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Optimal design of antireflection coating and experimental verification by plasma enhanced chemical vapor deposition in small displays

S. M. Yang, Y. C. Hsieh, and C. A. Jeng

J. Vac. Sci. Technol. A 27, 336 (2009); http://dx.doi.org/10.1116/1.3081962 (6 pages) | Cited 3 times

Online Publication Date: 27 February 2009

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Conventional antireflection coating by thin films of quarter-wavelength thickness is limited by material selections and these films’ refractive indices. The optimal design by non-quarter-wavelength thickness is presented in this study. A multilayer thin-film model is developed by the admittance loci to show that the two-layer thin film of SiNx/SiOy at 124/87 nm and three layer of SiNx/SiNy/SiOz at 58/84/83 nm can achieve average transmittances of 94.4% and 94.9%, respectively, on polymer, glass, and silicon substrates. The optimal design is validated by plasma enhanced chemical vapor deposition of N2O/SiH4 and NH3/SiH4 to achieve the desired optical constants. Application of the antireflection coating to a 4 in. liquid crystal display demonstrates that the transmittance is over 94%, the mean luminance can be increased by 25%, and the total reflection angle increased from 41° to 58°.
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42.79.Wc Optical coatings
42.15.Eq Optical system design
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

The direct injection of liquid droplets into low pressure plasmas

D. Ogawa, I. Saraf, A. Sra, R. Timmons, M. Goeckner, and L. Overzet

J. Vac. Sci. Technol. A 27, 342 (2009); http://dx.doi.org/10.1116/1.3081965 (10 pages) | Cited 1 time

Online Publication Date: 27 February 2009

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A much greater number of useful precursors for plasma-enhanced chemical vapor deposition (PECVD) can be dispersed in high vapor pressure solvents than can be put into the vapor phase directly. In order to enable the use of such precursors, the authors investigated a method by which one can directly inject these liquids as microdroplets into low pressure PECVD environments. The solvent evaporates first leaving behind the desired precursor in the gas/plasma. The plasma dissociates the vapor and causes the deposition of a composite film (from precursor, solvent, and plasma gas). The authors made preliminary tests using Fe nanoparticles in hexane and were able to incorporate over 4% Fe in the resulting thin films. In addition, the authors simulated the process. The time required for a droplet to fully evaporate is a function of the background pressure, initial liquid temperature, droplet-vapor interactions, and initial droplet size. A typical evaporation time for a 50 μm diameter droplet of hexane is ∼ 3 s without plasma at 100 mTorr. The presence of plasma can decrease the evaporation time by more than an order of magnitude. In addition, the model predicts that the temperature of the injected droplet first decreases by evaporative cooling (to ∼ 180 K for hexane); however, once the solvent has fully evaporated/sublimated, the plasma heats any remaining solute. As a result the solute temperature can first fall to 180 K, then rise to nearly 750 K in less than 1 s.
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68.03.Fg Evaporation and condensation of liquids
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
64.70.Hz Solid-vapor transitions
52.77.-j Plasma applications

Improved optical and electrical properties of rf sputtered Al doped ZnO films on polymer substrates by low-damage processes

Hyung Seob Min, Min Kyu Yang, and Jeon-Kook Lee

J. Vac. Sci. Technol. A 27, 352 (2009); http://dx.doi.org/10.1116/1.3081966 (4 pages) | Cited 2 times

Online Publication Date: 27 February 2009

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Three types of low-damage radio-frequency (rf) magnetron sputtering processes—an interruptive process, a rotating cylindrical holder method, and an off-axis sputtering method—were designed and studied to reduce the film surface temperature during deposition. Low-damage sputtering processes were investigated to improve the resistivity and optical transmittance in the visible range of Al doped ZnO (AZO) thin films deposited on polymer substrates. In the case of the polyethersulfone substrate, AZO films with a resistivity of 1.0×10−3 Ω cm and an optical transmittance of 75% were obtained by the rotating repeat holder method during rf sputtering.
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68.55.ag Semiconductors
81.15.Cd Deposition by sputtering
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
78.40.Fy Semiconductors

Velocity distribution function of sputtered gallium atoms during inductively coupled argon plasma treatment of a GaAs surface

Emilie Despiau-Pujo, Pascal Chabert, Raphaël Ramos, Gilles Cunge, and Nader Sadeghi

J. Vac. Sci. Technol. A 27, 356 (2009); http://dx.doi.org/10.1116/1.3081967 (6 pages) | Cited 4 times

Online Publication Date: 27 February 2009

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A GaN laser diode at 403.3 nm is used to measure the velocity distribution function (vdf) of Ga atoms sputtered from a radio-frequency biased GaAs substrate in a low pressure inductively coupled plasma (ICP) argon discharge. To investigate both perpendicular (Vz normal to wafer) and longitudinal (Vx parallel to wafer) velocity components, laser induced fluorescence (LIF) measurements are performed in the z direction and atomic absorption spectroscopy (AAS) in the x direction. The longitudinal vdf of Ga sputtered atoms is very close to a Lorentzian function with Vx comprised between 0 and 7500 m s−1, while the perpendicular velocities Vz can reach 10 000 m s−1. Experimental results are compared to molecular dynamics (MD) simulations of Ar+ ion sputtering of GaAs under 200 eV bombardment. MD predictions and experiments are in fairly good agreement, which confirms the existence of products sputtered from the surface with kinetic energies larger than 10 eV. In etching processes dominated by physical bombardment, these energetic atoms could alter passivation layers on sidewalls and be responsible for defects observed in nanodevices. The best fit of the Doppler-broadened LIF and AAS profiles with the vdfs predicted by sputtering theory allows one to estimate the surface binding energy of Ga atoms in GaAs, Eb, to be around 3 eV.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
78.55.Cr III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Oxygen incorporation and charge donor activation via subplantation during growth of indium tin oxide films

A. Amassian, M. Dudek, O. Zabeida, S. C. Gujrathi, J. E. Klemberg-Sapieha, and L. Martinu

J. Vac. Sci. Technol. A 27, 362 (2009); http://dx.doi.org/10.1116/1.3081970 (5 pages) | Cited 1 time

Online Publication Date: 27 February 2009

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The use of plasma assistance is shown to enhance the optoelectronic properties (i.e., transparency, free carrier density, and conductivity) of indium tin oxide (ITO) deposited by reactive magnetron sputtering by promoting the incorporation of oxygen in substoichiometric oxide films during magnetron sputtering. The authors demonstrate that subplantation of oxygen ions (O2+ and O+), i.e., their implantation to depths of several nanometers below the growth surface, is the primary pathway by which radio frequency plasma assistance at the substrate surface enhances oxygen incorporation during reactive magnetron sputtering of ITO. These conclusions are supported independently by elastic recoil detection measurements of ITO films in the time-of-flight regime and Monte Carlo TRIDYN simulations of oxygen ion bombardment in the reactive low-pressure plasma environment. The findings indicate that subplantation plays a crucial role in improving the optoelectronic properties of O-deficient ITO films.
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81.15.Cd Deposition by sputtering
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
52.77.Dq Plasma-based ion implantation and deposition
78.66.Jg Amorphous semiconductors; glasses
68.55.ag Semiconductors
73.61.Jc Amorphous semiconductors; glasses

Roughening during XeF2 etching of Si(100) through interface layers: H:Si(100) and a-Si/Si(100)

A. A. E. Stevens, M. C. M. van de Sanden, H. C. W. Beijerinck, and W. M. M. Kessels

J. Vac. Sci. Technol. A 27, 367 (2009); http://dx.doi.org/10.1116/1.3085718 (9 pages)

Online Publication Date: 27 February 2009

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Real-time spectroscopic ellipsometry has been applied in situ in an Ar+/XeF2 beam-etching experiment to study the roughening of Si(100) etched by XeF2 at room temperature. The role of initial surface conditions has been examined. For the etching of hydrogen-terminated (H:)Si(100), the roughness evolution as a function of XeF2 dose can be characterized by an initially fast roughening phase followed by a slower, final roughening phase. Similar behavior is observed when etching through an amorphous silicon (a-Si) layer on top of crystalline Si(100) bulk as obtained by sputter cleaning of Si(100) substrates. These observations can be explained as follows. Both H termination and a-Si lead to patch formation on the surface where etching is impeded and hence, high aspect-ratio etch pits develop. The quantitative differences in roughening can then be attributed to the duration and timing of the influence of the H-terminated and a-Si patches on the etch process until H-bonded Si surface atoms or a-Si are totally removed from the surface. Surface area increase due to the roughening can therefore be held responsible for observed trends and differences in etch rates, reaction layer thickness, and composition as a function of etch time.
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81.65.Cf Surface cleaning, etching, patterning
68.35.bj Amorphous semiconductors, glasses
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.47.Fg Semiconductor surfaces
68.35.Dv Composition, segregation; defects and impurities

Vacuum outgassing of high density polyethylene

L. N. Dinh, J. Sze, M. A. Schildbach, S. C. Chinn, R. S. Maxwell, P. Raboin, and W. McLean

J. Vac. Sci. Technol. A 27, 376 (2009); http://dx.doi.org/10.1116/1.3085719 (5 pages) | Cited 2 times

Online Publication Date: 27 February 2009

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A combination of thermogravimetric analysis and temperature programmed decomposition was employed to identify the outgassing species, the total amount of outgassing, and the outgassing kinetics of high density polyethylene (HDPE) in a vacuum environment. The isoconversional kinetic analysis was then used to analyze the outgassing kinetics and to predict the long-term outgassing of HDPE in vacuum applications at ambient temperature. H2O and CnHx, with n as high as 9 and x centering around 2n, are the major outgassing species from solid HDPE, but the quantities evolved can be significantly reduced by vacuum baking at 368 K for a few hours prior to device assembly.
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68.43.Vx Thermal desorption
64.75.-g Phase equilibria
82.20.-w Chemical kinetics and dynamics

Carbonitriding of silicon using plasma focus device

S. Jabbar, I. A. Khan, R. Ahmad, M. Zakaullah, and J. S. Pan

J. Vac. Sci. Technol. A 27, 381 (2009); http://dx.doi.org/10.1116/1.3085720 (7 pages)

Online Publication Date: 27 February 2009

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Carbonitride thin films have been deposited on silicon substrate by the irradiation of energetic nitrogen ions emanated from dense plasma focus device. The carbon ions are ablated by the irradiation of relativistic electrons from the insert material (graphite) placed at the anode tip. The x-ray diffraction analysis demonstrates that a polycrystalline thin film consisting of various compounds such as Si3N4, SiC, and C3N4 is formed on the silicon (100) substrate. Crystallinity of different compounds decreases with the increase in angular positions (0°, 10°, and 20°). Raman spectroscopy shows the appearance of graphitic and disordered bands with silicon nitride and silicon carbide indicating the formation of carbonitride. Raman spectra also indicate that broadening of bands increases with the increase in focus deposition shots, leading to the amorphization of the thin film. The amorphization of the thin films depends on the ion energy flux as well as on the sample angular position. The scanning electron microscopy exhibits the damaging of the substrate surface at 0° angular position. The microstructure shows the tubular shape for higher ion dose (40 focus shots). At 10° angular position, a two phase phenomenon is observed with the ordered phase in the solid solution. A smooth and uniform surface morphology showing a small cluster is observed for the 20° angular position.
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68.55.ag Semiconductors
61.80.Jh Ion radiation effects
68.35.B- Structure of clean surfaces (and surface reconstruction)
52.58.Lq Z-pinches, plasma focus, and other pinch devices
81.15.Jj Ion and electron beam-assisted deposition; ion plating
78.30.Hv Other nonmetallic inorganics

Mixing-layer kinetics model for plasma etching and the cellular realization in three-dimensional profile simulator

Wei Guo, Bo Bai, and Herbert H. Sawin

J. Vac. Sci. Technol. A 27, 388 (2009); http://dx.doi.org/10.1116/1.3085722 (16 pages) | Cited 10 times

Online Publication Date: 27 February 2009

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In this article the major kinetics models for plasma-surface interactions were reviewed highlighting their strengths and limitations. As a subset of reactive-site modeling, mixing-layer kinetics model was developed based upon the assumption of random atomic mixing in the top surface layer. The translation of the layer enabled the modeling of both etching and deposition. A statistical concept, nearest-neighbor bonding probability, was defined to express the concentration of any surface moieties with the surface elemental composition. A lumped set of reactions was adopted to carry on the overall physichemical processes including ion incorporation, neutral adsorption, physical sputtering, ion-enhanced etching, dangling bond generation and annihilation, and spontaneous etching. The rate coefficients were fitted to the experimental etching yields at various beam etching conditions. The good match between the kinetics modeling and the experimental results verified the capability of the mixing-layer model of predicting the poly-Si etching in chlorine plasma at various operating conditions. Then the kinetics model was incorporated into the three-dimensional Monte Carlo profile simulator. The concept of the mixing layer was simulated by a cellular-based model through composition averaging among neighboring cells. The reactions were sorted out in terms of ion initiated and neutral initiated, respectively, as discrete events. The reaction rates were calculated based upon the cellular composition and used as probabilities to remove particles from the cell. Results showed that the profile simulation combined with the kinetics, the numeric kinetics model, and the experimental etching yields are in quantitative agreement, which demonstrated the accuracy of kinetics after incorporation into the profile simulation. The simulation was compared to the published research work comprehensively including the etching yields, surface compositions, and dominant product distributions.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.77.Bn Etching and cleaning
52.65.Pp Monte Carlo methods
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Gas jet assisted vapor deposition of yttria stabilized zirconia

D. D. Hass and H. N. G. Wadley

J. Vac. Sci. Technol. A 27, 404 (2009); http://dx.doi.org/10.1116/1.3085725 (11 pages) | Cited 2 times

Online Publication Date: 27 February 2009

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A gas jet assisted electron beam evaporation process for synthesizing yttria stabilized zirconia (YSZ) coatings has recently been reported. The process uses a rarefied inert gas jet to entrain and transport vapor to a substrate. The gas jet enables the lateral spreading of the flux to be controlled and large fractions of the vapor to be deposited on samples of relatively small size. When the gas pressure is high, coatings grown at 1050 °C and below have a columnar structure and a high pore fraction. The total pore volume fraction, the morphology of the inter- and intracolumn pores and the coating texture are all observed to be a strong function of the gas pressure in the chamber with increasing chamber pressure leading to larger intercolumnar pore spacings, wider pores, a higher total pore volume fraction, and a reduction in the coating texture. A direct simulation Monte Carlo simulation approach has been used to investigate vapor transport for the various gas pressures explored in this study. The simulation indicates that as the gas pressure increases, binary scattering events between the vapor and background gas broaden the vapor molecule incidence angle distribution. This intensifies flux shadowing and results in the incorporation of voids in the coating. Increasing the gas pressure also results in a rapid increase in the vapor phase nucleation of YSZ clusters. This observation coincides with a transition from a [200] textured columnar morphology at moderate pressures to a nanogranular structure with no texture and a very high nanoscopic pore volume fraction at high pressures.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.jm Texture
68.35.bt Other materials
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Erratum: “Profile evolution simulator for sputtering and ion-enhanced chemical etching” [ J. Vac. Sci. Technol. A 27, 130 (2008) ]

J. Saussac, J. Margot, and M. Chaker

J. Vac. Sci. Technol. A 27, 415 (2009); http://dx.doi.org/10.1116/1.3085733 (1 page)

Online Publication Date: 27 February 2009

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Abstract Unavailable
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99.10.Cd Errata
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