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Jan 1993

Volume 11, Issue 1, pp. 1-271


Preparation and characterization of crystalline ZrC films

T. C. Tessner and P. R. Davis

J. Vac. Sci. Technol. A 11, 1 (1993); http://dx.doi.org/10.1116/1.578703 (5 pages) | Cited 2 times

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The characterization of the surface properties of ZrC films grown by thermally evaporating ZrC onto room temperature W(100)and W(110) and then annealing, are reported. These films as deposited have no long range order as determined by low energy electron diffraction, but heating to above 1800 K produces well‐ordered layers. During annealing the ZrC(100) face forms on W(100), and the ZrC(111) face forms on W(110). Work functions as low as 2.75 eV have been measured on these films after initial heating, but final values are 3.85 eV for ZrC(100), and from 4.40 to 4.80 eV for ZrC(111), depending on the C contamination of the W(110) substrate. From thermal desorption spectra desorption energies were also calculated. Possible mechanisms for the ZrC crystalline ordering during annealing are discussed.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
79.40.+z Thermionic emission
73.30.+y Surface double layers, Schottky barriers, and work functions

Surface and interface effects in WSi2 formation

J. P. W. B. Duchateau, A. E. T. Kuiper, E. G. C. Lathouwers, and A. H. Reader

J. Vac. Sci. Technol. A 11, 6 (1993); http://dx.doi.org/10.1116/1.578722 (5 pages) | Cited 1 time

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We studied the influence of a thin Fe interface layer between W and the substrate Si and of a surface W–oxide on the formation kinetics of WSi2. Auger depth profiling, Rutherford backscattering spectrometry and x‐ray diffraction have been used to investigate the reaction between the layers and the Si substrate. W layers with a thickness of 20 nm were deposited by electron beam evaporation on HF dipped Si(100) samples. If deposition and subsequent annealing are performed in ultrahigh vacuum, the complete conversion of a W layer into tetragonal WSi2 occurs within 1 h at 800 °C. The intercalation of a 5 nm‐thick Fe layer between the W layer and the substrate reduces the conversion temperature to 650 °C. Ironsilicide is formed at a relatively low temperature. This silicide acts as a medium through which Si can easily diffuse towards the surface, thus maintaining a fast Si supply to the W layer. This experiment indicates that reactions at the metal/Si interface are rate determining in the formation of WSi2. Both with and without an Fe intermediate layer, the reaction proceeds via the migration of Si to the film surface followed by the formation of WSi2 at the surface. Continuation of the reaction occurs from the surface to the substrate. Furthermore, we found that the presence of a native oxide layer at the W surface retards the reaction between W and Si. Oxygen migrates via the open structure of the W film to the interface where it probably forms a thin SiO2 layer that hampers the transport of Si into the W film.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Fx Diffusion; interface formation

Interfacial reactions in epitaxial Al/Ti1−xAlxN (0≤x≤0.2) model diffusion‐barrier structures

I. Petrov, E. Mojab, F. Adibi, J. E. Greene, L. Hultman, and J.‐E. Sundgren

J. Vac. Sci. Technol. A 11, 11 (1993); http://dx.doi.org/10.1116/1.578277 (7 pages) | Cited 13 times

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Transmission electron microscopy (TEM), cross‐sectional TEM, scanning TEM with energy dispersive x‐ray analysis, and Auger electron spectroscopy were used to investigate the nature of rate‐controlling interfacial reactions in epitaxial Al/Ti1−xAlxN thin‐film couples. TiN and NaCl‐structure Ti1−xAlxN layers, 120 nm thick, with compositions x=0.1 and 0.2 were grown on MgO(001) substrates by ultrahigh vacuum reactive magnetron cosputter deposition in N2 discharges. Epitaxial Al films, 200‐nm‐thick, were then grown in Ar on top of the nitride layers during the same vacuum cycle. The reaction paths for Al/TiN and Al/(Ti,Al)N interactions during anneals at Ta=600 °C for ta up to 150 min was similar, but the extent of reaction was dramatically decreased by the substitution of (Ti,Al)N barrier layers for TiN. The primary mobile species during annealing was Ti which penetrated into the Al layers and reacted to form the ordered tetragonal intermetallic phase Al3Ti while Al segregation resulted in the formation of a narrow metastable zincblende structure AlN layer at the Al/nitride interface. The room‐temperature resistivity of 1‐μm‐thick nitride layers varied from 15 μΩ cm for TiN to 60 μΩ cm for Ti0.8Al0.2N.
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68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers

Photoassisted growth of gallium nitride by gas source molecular beam epitaxy

M. J. Paisley and R. F. Davis

J. Vac. Sci. Technol. A 11, 18 (1993); http://dx.doi.org/10.1116/1.578700 (7 pages)

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Thin films of GaN have been achieved via gas source molecular beam epitaxy with and without substrate illumination from a 500 W Hg arc lamp. X‐ray photoelectron spectroscopy showed a nominally stoichiometric GaN film without contaminants regardless of illumination. Illumination and Ga cell temperature changed the texture of the polycrystalline GaN from (0001)∥(100) to (0001)∥(111) and back again. Near single crystal films were deposited with an orientation relationship of w‐GaN (0001)∥β‐SiC (100) and (101̄0)∥(011̄). Resulting films were characterized by scanning electron microscopy as well as x‐ray and electron diffraction.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Low‐pressure ion nitriding of AISI 304 austenitic stainless steel with an intensified glow discharge

E. I. Meletis and S. Yan

J. Vac. Sci. Technol. A 11, 25 (1993); http://dx.doi.org/10.1116/1.578712 (9 pages) | Cited 11 times

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Low‐pressure ion nitriding of AISI 304 austenitic stainless steel was conducted in the present study by intensifying the glow discharge. Plasma intensification was produced by thermionic emission and by utilizing a triode glow discharge system. The results showed that under the intensified plasma conditions, effective nitriding can be accomplished at relatively low temperatures. The nitride layer had a dense structure, high purity and an ultrafine microstructure with a grain (nucleus) size less than 80 Å. The nitriding treatment produced a thin layer of high nitrides (FeN and Fe2N) followed by a diffusion controlled layer of (Fe,Cr)3N. X‐ray and electron‐diffraction analysis showed that all nitrides were hexagonal in crystal structure. The intensified plasma treatment caused a significant increase in the nitride layer growth kinetics. The enhancement of the nitrogen diffusion was attributed to the higher surface concentration of vacancies due to the energetic particle bombardment and to grain boundary diffusion in the nitride phase. A simplified diffusion model is developed to estimate the effective nitrogen diffusivity under the intensified plasma ion nitriding.
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81.05.Bx Metals, semimetals, and alloys
68.35.Gy Mechanical properties; surface strains
68.35.Dv Composition, segregation; defects and impurities
68.35.Fx Diffusion; interface formation

Effects of ion bombardment in plasma etching on the fluorinated silicon surface layer: Real‐time and postplasma surface studies

Gottlieb S. Oehrlein

J. Vac. Sci. Technol. A 11, 34 (1993); http://dx.doi.org/10.1116/1.578717 (13 pages) | Cited 27 times

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The silicon–fluoride reaction layer formed on silicon surfaces when etched in low pressure discharges of CF4 and SF6 has been characterized using ellipsometry in real time and x‐ray photoemission spectroscopy (XPS) after sample transfer in vacuum. By comparing reactive ion etching (sheath voltage Vs=50–500 eV) and plasma etching (Vs≂30 eV) over the pressure range 10–250 mTorr and by using different rf power levels, the effects of ion bombardment on the SiFx layer were examined. The thickness of the SiFx layer depends primarily on the sheath voltage of the discharge, which determines the maximum energy of the bombarding ions. For low ion bombardment etching the apparent thickness of the SiFx layer is ≂0.5 nm. It increases up to ≂1.7 nm as the sheath voltage is increased. Nondestructive profiling of the SiFx layer was performed by angle‐resolved photoemission to determine the variation of the various fluorosilyls (SiF, SiF2, SiF3, and SiF4) as a function of depth. SiF3 has the highest intensity at the surface of the SiFx layer and drops off rapidly in relative importance as the reacted layer is probed deeper. At the largest depth, SiF becomes the dominant species. SiF2 and SiF4 are also peaked at the surface, but their relative importance is always smaller than that of SiF and SiF3. The initial stages of fluorination of the Si surface were monitored in real time using ellipsometry. Within the first seconds of exposure to the plasma, a damaged Si layer is introduced which is subsequently fluorinated and partly consumed. The steady‐state SiFx layer thus formed and present on the crystal during etching is stable when the discharge is terminated. This finding validates the use of postplasma XPS analysis for the study of the SiFx layer. The ellipsometric measurements demonstrate that an increase in the sheath voltage of the discharge results in increased surface damage and deeper fluorination of the Si surface. These results are in conflict with the predictions of several models of ion‐enhanced etching and indicate that ion‐induced mixing and generation of damage may play an important role in ion‐enhanced etching reactions.
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81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Thermal oxidation of TiN studied by means of soft x‐ray absorption spectroscopy

L. Soriano, M. Abbate, J. C. Fuggle, P. Prieto, C. Jiménez, J. M. Sanz, L. Galán, and S. Hofmann

J. Vac. Sci. Technol. A 11, 47 (1993); http://dx.doi.org/10.1116/1.578718 (5 pages) | Cited 9 times

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The oxidation of TiN in an oxygen flow at temperatures in the range 300–500 °C has been studied by means of soft x‐ray absorption spectroscopy. The analysis of the experimental results indicates that O progressively displaces N to form TiO2. The process appears to be controlled by the temperature dependence of the oxygen diffusion. Some oxidation is observed to take place even at room temperature. No evidence of oxynitride formation was found in thermally oxidized TiN, instead complete phase separation is observed. The interface between TiO2 and TiN seems to be very abrupt. The appearance of a sharp absorption peak in the N 1s spectrum of TiN is believed to be due to nitrogen atoms which are displaced during the oxidation process and remain unbounded within the TiO2 matrix. For temperatures above 400 °C, this peak disappears as the interstitial N atoms migrate to the surface and desorb.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
82.30.Nr Association, addition, insertion, cluster formation

Chemistry of S/GaAs and metal/S/GaAs systems

Hirohiko Sugahara, Masaharu Oshima, Haruhiro Oigawa, and Yasuo Nannichi

J. Vac. Sci. Technol. A 11, 52 (1993); http://dx.doi.org/10.1116/1.578719 (6 pages) | Cited 10 times

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Bonding states and the band bending of S/n‐GaAs (001) and metal/S/n‐GaAs (001) systems are studied by synchrotron radiation photoemission spectroscopy (SRPES). The difference in the surface chemistry between the (NH4)2Sx‐treated GaAs and the sulfur‐chemisorbed GaAs is explained well by the formation of the sulfur‐rich transition layer for the (NH4)2Sx‐treated GaAs. A structural model for the annealed S/GaAs (001) system is proposed, in which the surface is terminated with Ga–S bonds. The barrier height of the Al, Au, and In Schottky contacts on (NH4)2Sx‐treated n‐GaAs is also determined to be about 0.4, 0.7, and 0.3 eV, respectively, by SRPES for the first time, which are in fairly good agreement with I–V characteristics of the metal/S/n‐GaAs Schottky diodes. It is found that the oxide‐free interface with a sulfur interlayer plays an important role for the metal‐dependent Schottky barrier formation.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.65.-b Surface treatments
73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.At Surface states, band structure, electron density of states

Mixing effects in CeO2/TiO2 and CeO2/SiO2 systems submitted to Ar+ sputtering

A. R. González‐Elipe, A. Fernández, J. P. Holgado, A. Caballero, and G. Munuera

J. Vac. Sci. Technol. A 11, 58 (1993); http://dx.doi.org/10.1116/1.578720 (8 pages) | Cited 2 times

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Mixing effects induced in CeO2/TiO2 and CeO2/SiO2 composite powdered materials by bombardment with Ar+ ions of 3.5 keV of kinetic energy have been studied by x‐ray photoelectron spectroscopy (XPS) and the factor analysis method. Characterization of the ceria phase in the original composite samples was carried out by x‐ray diffraction (XRD) temperature programmed reaction, transmission electron microscopy, and extended x‐ray absorption fine structure. The CeO2/SiO2 sample is characterized by very small domains (∼25 Å in size) where the cerium has entered the Si–O lattice forming a kind of silicatelike amorphous phase. In CeO2/TiO2 the cerium is in a bimodal distribution with small particles of CeO2 (30–100 Å in size) and a cerium oxide phase formed by very small particles (d=16 Å) well dispersed on the TiO2 grains. XPS showed that either by heating in H2 or by Ar+ sputtering a Ce4+→Ce3+ reduction occurs to an extent which depends on the sample and reduction conditions. The reduction degree, determined from the XPS spectra by the factor analysis method, decreased in the sense CeO2/SiO2≳CeO2/TiO2≳ CeO2, for each sample being always higher after Ar+ sputtering than after heating in H2. Adsorption of O2 at 373 K on the reduced samples led to their partial reoxidation, to an extent which was dependent on the structure of the cerium in the samples and on the type of the previous reduction treatment. In the case of the CeO2/TiO2 sample the high reduction degree obtained by Ar+ sputtering can be explained by assuming a mixing of the cerium and titanium oxide phases induced by the ion bombardment. The use of a chemical probe such as the adsorption of O2 is proposed as a method to detect the existence of mixing phenomena in composite systems submitted to ion bombardment.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Copper metalorganic chemical vapor deposition reactions of hexafluoroacetylacetonate Cu(I) vinyltrimethylsilane and bis (hexafluoroacetylacetonate) Cu(II) adsorbed on titanium nitride

V. M. Donnelly and M. E. Gross

J. Vac. Sci. Technol. A 11, 66 (1993); http://dx.doi.org/10.1116/1.578721 (12 pages) | Cited 14 times

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Cu is receiving increasing attention as a replacement for Al in future Si ultra‐large‐scale integrated circuits due to its lower resistivity and potentially better reliability in terms of electromigration resistance and stress‐induced voiding. Metalorganic chemical vapor deposition (MOCVD) of Cu offers the advantages of conformal coverage and selective growth. Whatever the means of deposition, a diffusion barrier and adhesion layer such as TiN is required. To understand the nucleation mechanisms of Cu film growth on TiN during MOCVD, we have studied the thermal decomposition of two metalorganic precursors, hexafluoroacetylacetonate Cu(I) vinyltrimethylsilane [CuI(hfac)(vtms)], and bis (hexafluoroacetylacetonate) Cu(II) [CuII(hfac)2] by x‐ray photoelectron spectroscopy and temperature programmed desorption mass spectrometry in an ultrahigh vacuum (UHV) system.
Experiments were carried out on polycrystalline air‐exposed (i.e., oxidized) TiN and N2 ion beam sputter‐cleaned TiN. These surfaces are representative of those found in the traditional stand‐alone and newer integrated metallization processing sequences, respectively. Room temperature dosing of TiN with CuI(hfac)(vtms) is accompanied by rapid desorption of the vtms ligand, leaving chemisorbed CuI(hfac). This CuI(hfac) decomposes upon heating to form CO, CO2 and CF4 desorption products, leaving about 90% of the Cu on the surface, along with some F and C. CII(hfac)2 also dissociatively chemisorbs at room temperature to form CuI(hfac) and an adsorbate with the stoichiometry of hfac. Unlike CuI(hfac)(vtms), a Cu(hfac)‐containing species desorbs upon heating above 75 °C. Near 200 °C this process ceases and decomposition (and possibly some intact desorption) of hfac takes place, leading to desorption of CO, CO2, and CF4. After desorption of all C‐containing species, about 30% of the initially deposited Cu remains on the surface, along with a submonolayer coverage of F. Regardless of the precursor, Cu begins to diffuse into the TiN film, above 280 °C. The results of our studies offer insights into the different mechanisms that may play a role in the nucleation of MOCVD film growth and incorporation of impurities at the interface. Significantly, the disproportionation reaction that dominates the deposition of pure Cu from CuI(hfac)(vtms) at the higher pressures typical of MOCVD does not occur under UHV conditions.  
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Influence of surface‐activated reaction kinetics on low‐pressure chemical vapor deposition conformality over micro features

Julian J. Hsieh

J. Vac. Sci. Technol. A 11, 78 (1993); http://dx.doi.org/10.1116/1.578723 (9 pages) | Cited 6 times

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The coupled effect of molecular scattering and surface‐activated reactions on low‐pressure chemical vapor deposition (LPCVD) film conformality is investigated. Using a single‐precursor two‐step surface‐activated deposition as an example, film conformality can be found to depend on two first‐principle dimensionless parameters–Sc, the intrinsic sticking coefficient, and Sa, the surface saturation factor. An analytical integral material balance formulation, developed for the feature‐scale molecular transport, is solved numerically in a wide range of Sc and Sa. The results show that film conformality generally improves with decreasing Sc and increasing Sa. With Sc fixed in most LPCVD processes (due to the nature of the precursor species), the ability to control Sa in the process becomes the key to conformal deposition. The intrinsic surface‐activated deposition rate expression shows no apparent reaction order. Therefore, previously reported Monte Carlo schemes and integral‐differential models employing a single sticking parameter or a fixed reaction order to characterize LPCVD step coverage behavior are applicable only in limited cases. The two‐parameter model has been found useful in understanding the H2‐reduced tungsten CVD process, for which the first‐principle parameters can be determined from kinetic data reported in the literature.  
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Comparison of mechanical and microstructural properties of hydrogen and silane reduced low pressure chemical vapor deposited tungsten films

S. Sivaram, M. L. A. Dass, C. S. Wei, B. Tracy, and R. Shukla

J. Vac. Sci. Technol. A 11, 87 (1993); http://dx.doi.org/10.1116/1.578724 (9 pages) | Cited 5 times

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We have compared the physical, mechanical, microstructural, and structural properties of tungsten thin films produced by reducing tungsten hexaflouride by silane and hydrogen. We show that despite similarities in chemical composition and film density, the films exhibit differing film hardness and elastic compliances. The origin of the differences is shown to arise from the differences in film growth rate and the incorporation of impurities during film growth. Hydrogen reduction results in the formation of second phase W20O58 particles in the tungsten bulk, which leads to film hardening. Silane reduced films show strong texture in the [110] direction, which decays with increasing film thickness. Silane films also show a larger tensile stress and faulted microstructure. Extensive transmission electron microscopy analysis has been carried out and the results have been correlated to x‐ray diffraction studies. We also have studied the surface morphology of the films and show clustering of grains which results in a larger surface feature, compared to the average grain size of the film. As a result of this study, we show the need to complete film characterization prior to changing chemistries to meet specific macroscopic film properties such as film step coverage.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties

Tungsten and tungsten–carbon thin films deposited by magnetron sputtering

Ph. Gouy‐Pailler and Y. Pauleau

J. Vac. Sci. Technol. A 11, 96 (1993); http://dx.doi.org/10.1116/1.578725 (7 pages) | Cited 12 times

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Tungsten and tungsten–carbon thin films have been produced from a W target sputtered in argon and argon–methane mixtures, respectively. The deposition rate of W films was measured as a function of the sputtering power and argon pressure varying in the range of 0.3–3 Pa. The crystallographic structure and composition of W films deposited on silicon and carbon substrates were investigated by x‐ray diffraction and Rutherford backscattering spectroscopy. The electrical resistivity of the W films was minimum (12 μΩ cm) when the internal stresses in the films were negligible. The carbon concentration in the W–C films determined by nuclear reaction analyses and Rutherford backscattering spectroscopy was varied from 10 to 95 at. % with increasing CH4 content in the gas phase. The crystallographic structure of the W–C films was found to be dependent on the carbon concentration. Below 25 at. % of carbon, the structure of the W–C films was that of the cubic α‐W phase with a dilated lattice parameter. For higher carbon concentrations, the bcc α‐W phase disappeared and the structure was that of the nonstoichiometric cubic β‐WC1−x phase. The structure of W–C films with a carbon content greater than 65 at. % was nearly amorphous. Internal stresses and electrical resistivity of W–C films were determined as functions of the carbon concentration. The experimental parameters suitable to produce W and W–C films with low resistivities and reduced internal stress level are reported in this article.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys

Characterization of electron cyclotron resonance plasmas optimized for the deposition of polycrystalline diamond films

D. L. Youchison, C. R. Eddy, and B. D. Sartwell

J. Vac. Sci. Technol. A 11, 103 (1993); http://dx.doi.org/10.1116/1.578275 (12 pages) | Cited 14 times

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Optical emission spectroscopy, Langmuir probes, and B‐field probes have been used to characterize electron cyclotron resonance plasmas used in the deposition of polycrystalline diamond films. These plasmas were generated at 1.33 Pa using selected ratios of CO:H2 and CH4:O2:H2 that produced the highest quality films (i.e., high degree of faceting and an intense Raman peak at 1332 cm−1). Electron temperature, ion density, plasma potential and B‐field profiles obtained at optimum growth conditions are presented. The best diamond films were produced on silicon (100) substrates biased to +40 V dc and maintained at a constant temperature of 500 °C. These substrates were placed downstream of an electron cyclotron resonance (ECR) layer (the region of high plasma density created by resonant microwave absorption at the 87.5 mT B‐field contour), characterized by a Te near 1 eV and ion densities near 4×1012 cm−3. Actinometry was used to quantify the optical emission spectra. In the CO:H2 system, quality films were obtained for line intensity ratios of Hγ/Ar=4.0, Hγ/C2=1.1, CH/C2=1.9, CO/C2=0.73, and O/C2=0.89. Nearly identical films were produced in the CH4:O2:H2 system, with line intensity ratios of Hγ/Ar=4.2, Hγ/C2=1.2, CH/C2=1.5, CO/C2=0.78, O/C2=0.99. These results indicate that feedgas composition is less important than the critical ratios of C/O/H2 in an ECR plasma.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Ds Electric and magnetic measurements

Characterization of sputter deposited inconel/carbon x‐ray multilayers

M. S. Aouadi, R. R. Parsons, P. C. Wong, and K. A. R. Mitchell

J. Vac. Sci. Technol. A 11, 115 (1993); http://dx.doi.org/10.1116/1.578276 (10 pages) | Cited 1 time

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The reflectivity of x‐ray multilayers made of new pairs of materials was theoretically calculated at a wavelength of 45 Å. Carbon and inconel were then selected for ‘‘low index’’ and ‘‘high index’’ layers, respectively, in the multilayer system. Single layers, bilayers, and multilayers of carbon and inconel were characterized by grazing x‐ray reflectometry (GXR), x‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and spectroscopic ellipsometry (SE). From GXR data at 1.54 Å refractive indices and film thicknesses of inconel and carbon layers were obtained. From an analysis of SE data, the dielectric function and the thickness as of inconel and carbon thin films were deduced. XPS and AES measurements revealed the presence of carbides at the interface between carbon and inconel. GXR analysis was performed on ten‐layer C/inconel multilayers. The GXR interference pattern was found to broaden after annealing the samples at 600 °C.
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78.66.Bz Metals and metallic alloys
78.70.Ck X-ray scattering
42.79.Fm Reflectors, beam splitters, and deflectors

Postionization of sputtered neutrals by a focused electron beam

H.‐U. Gersch and K. Wittmaack

J. Vac. Sci. Technol. A 11, 125 (1993); http://dx.doi.org/10.1116/1.578278 (11 pages) | Cited 2 times

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We have explored a novel approach of electron‐impact postionization involving the use of a focused low‐energy electron beam directed at the flux of sputtered particles in very close proximity to the sample surface [‘‘matched’’ e‐beam sputtered neutral mass spectrometry (SNMS)]. The first version of an electron gun developed for this purpose delivers a 300 eV beam of ∼100 μA into a 100 μm spot. The postionization efficiency was investigated in a quadrupole based ion microprobe using samples of germanium and gallium arsenide bombarded with 10 keV Ar+. Singly and multiply charged species Mn+ (with n up to 5 for As) were produced by electron impact. The position and size of the electron beam with respect to the ion beam could be controlled and optimized by recording raster scanning ion images of the postionized species. Inspection of the energy spectra showed that the ionization probability is larger the lower the velocity of the sputtered neutrals. At low energies (<5 eV) and with the maximum electron current density presently achievable, the intensity ratio of singly charged postionized atoms to secondary ions was ≊1 for Ge and ≊5 for As. Fractional ion yields of 2×10−8 and 3×10−8, respectively, are estimated for these species. These numbers are higher by more than one order of magnitude than the yields obtained previously by ‘‘remote’’ e‐beam SNMS. Interference with the secondary ion flux was small or negligible in the case of doubly and multiply charged ions. The fractional ion yields for doubly charged ions ranged from 3 to 5×10−9. The results are compared with available cross sections for electron impact ionization. The measured SNMS ion yields are briefly compared with yields that can be achieved by charge transfer ionization using Ar+ beams at maximum current density. Advantages and limitations of the matched e‐beam SNMS technique are discussed together with conceivable improvements using a more advanced electron gun and an improved ionization and ion extraction geometry.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
34.80.Dp Atomic excitation and ionization

Design and characterization of a compact two‐target ultrahigh vacuum magnetron sputter deposition system: Application to the growth of epitaxial Ti1−xAlxN alloys and TiN/Ti1−xAlxN superlattices

F. Adibi, I. Petrov, J. E. Greene, U. Wahlström, and J.‐E. Sundgren

J. Vac. Sci. Technol. A 11, 136 (1993); http://dx.doi.org/10.1116/1.578279 (7 pages) | Cited 9 times

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The design, fabrication, and operation of a compact, portable, ultrahigh vacuum, two‐target magnetron sputter deposition system, consisting of independently pumped sample‐exchange and deposition chambers, is described. The target‐to‐substrate distance is 12.5 cm and, for alloy or superlattice growth, the substrate is typically placed at 45° to both target surfaces. A novel shutter system composed of a hollow cylinder with a rectangular opening is mounted on a rotary feedthrough driven by a precision direct‐current motor to controllably expose the substrate to sputter‐ejected flux from one or both targets. Film thickness and composition uniformity are achieved through the use of selectively transmitting shields which are first coated with target material to prevent film contamination. Automatic mass‐flow controllers, responding to a differential feedback signal from a capacitance manometer, are used to maintain the pressure constant during deposition. The film growth temperature can be varied from ambient to 1000 °C while adjusting the negative substrate bias from 0 to 500 V. In initial experiments using this system, epitaxial metastable Ti1−xAlxN alloys and TiN/Ti1−x AlxN superlattices were grown on MgO(001) and polycrystalline Ti1−xAlxN alloys were deposited on oxidized Si(001) substrates.
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81.15.Cd Deposition by sputtering
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Influence of the discharge frequency (35 kHz and 13.56 MHz) on the composition of plasma enhanced chemical vapor deposition a‐C:H films

C. Gómez‐Aleixandre, O. Sánchez, and J. M. Albella

J. Vac. Sci. Technol. A 11, 143 (1993); http://dx.doi.org/10.1116/1.578280 (4 pages) | Cited 5 times

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Amorphous carbon films have been deposited by plasma enhanced chemical vapor deposition from methane and hydrogen gas mixtures excited at two different frequencies, 35 kHz and 13.56 MHz. Large differences observed in the optical emission spectra of the discharge have been attributed to changes in the main dissociative excitation processes of the CH4 molecules. The deposition rate and film composition also depend on the discharge frequency. At 35 kHz, the high concentration of atomic hydrogen during the excitation process favors the etching of the amorphous carbon and extremely thin films are obtained. However, at 13.56 MHz, the deposition rate is much higher and the films present a high polymeric content, which has been related to one of the dissociative mechanism proposed at this frequency (i.e., CH4+e→CH2+H2+e).
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Electromagnetic fields in a radio‐frequency induction plasma

J. Hopwood, C. R. Guarnieri, S. J. Whitehair, and J. J. Cuomo

J. Vac. Sci. Technol. A 11, 147 (1993); http://dx.doi.org/10.1116/1.578281 (5 pages) | Cited 83 times

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The electromagnetic fields which drive a radio‐frequency induction plasma are both modeled and measured. The plasma source consists of a planar, square coil separated from a low pressure plasma chamber by a 2.54‐cm‐thick quartz window. A small loop antenna, which is sealed in a pyrex tube, is immersed in the discharge to determine the magnitude and direction of the rf magnetic field. The measured B field is primarily radial and axial. Typical rf field strengths vary from 2 to 7 G for rf powers of 0.1–1 kW. The radial B field decays exponentially in the axial direction. The skin depth of the electromagnetic field is 1.6–3.6 cm which is consistent with Langmuir probe measured ion densities (typically 3×1011 cm−3) in argon. Invoking Maxwell’s equations to deduce the rf electric field from the measured B field, we find the E field to be primarily azimuthal. Peak field strengths increase from 100 V/m at 100 W to 200 V/m at 600 W where they saturate for higher powers. Finally, we present a 3D finite element solution for the fields produced by this plasma source which employs a cold, collisionless plasma model to relate the relative plasma permittivity εr to the electron plasma frequency, ωpe, using εr=1−(ωpe/ω)2. The measured fields support this numerical solution.
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52.50.Dg Plasma sources
52.70.Ds Electric and magnetic measurements
52.80.Yr Discharges for spectral sources (including inductively coupled plasma)

Langmuir probe measurements of a radio frequency induction plasma

J. Hopwood, C. R. Guarnieri, S. J. Whitehair, and J. J. Cuomo

J. Vac. Sci. Technol. A 11, 152 (1993); http://dx.doi.org/10.1116/1.578282 (5 pages) | Cited 117 times

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In this work a planar, radio frequency induction plasma source is characterized in terms of ion density, electron temperature, and plasma potential using a single Langmuir probe in oxygen and noble gases. Probe measurements of density were also verified using microwave interferometry. Measured argon ion densities increase nearly linearly with power from 1×1011 cm−3 at 300 W rf power to 6×1011 cm−3 at 1.2 kW at 1×10−3 Torr. Krypton ion densities are also linear with power but saturate above 1 kW at a density of 2×1012 cm−3 at 1×10−3 Torr. Electron temperatures increase with decreasing pressure from 3 eV at 26×10−3 Torr to 7 eV at 0.3×10−3 Torr. Plasma potentials are typically 15–30 V and increase with decreasing pressure. Ion saturation current in oxygen at 5×10−3 Torr is 2.5% uniform over diagonals of 20 cm when a magnetic multipole bucket is used to confine the plasma. Ion generation energy cost in argon is 100–250 W/A.
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52.25.Jm Ionization of plasmas
52.70.Ds Electric and magnetic measurements
52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
52.50.Dg Plasma sources

Ion energy distribution functions in a multipole confined argon plasma diffusing from a 13.56‐MHz helicon source

C. Charles

J. Vac. Sci. Technol. A 11, 157 (1993); http://dx.doi.org/10.1116/1.578283 (7 pages) | Cited 21 times

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Ion energy distribution functions (IEDFs) are measured in a low‐pressure multipole confined diffusion plasma produced by a 13.56‐MHz helicon source and compared with the nonconfined case. The plasma confinement is efficient below 1‐μbar pressure and induces a plasma density increase of a factor of 2 in the diffusion region. Uniform radial profiles over 15 cm diam are obtained at the bottom of the diffusion chamber. The presence of the magnetized wall has a major effect on the IEDFs at 0.5‐ and 1‐μbar pressure conditions at distances over 10 cm from the source exit. The tail of the IEDFs, which corresponds to hot ions coming direct from the source to the bottom of the diffusion chamber, is not affected by the confinement. However, the peak of the IEDFs, which corresponds to the background density, is drastically increased due to the reflection of the ions on the magnetized wall. The ion collisionality, involving resonant charge exchange with neutrals, is enhanced by the confinement: the first reflection on the magnetized wall induces a longer path length in the diffusion area before recombination on the nonmagnetized bottom wall resulting in a better thermalization of the hot ions diverging from the source at very low pressures.
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52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
52.25.Fi Transport properties

Affecting factors on surface‐wave‐produced plasma

K. Komachi

J. Vac. Sci. Technol. A 11, 164 (1993); http://dx.doi.org/10.1116/1.578284 (4 pages) | Cited 16 times

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Distribution of surface‐wave‐produced plasmas and profiles of electric field on a dielectric line under plasma production were measured using a surface‐wave‐plasma (SWP) applicator with a plasma area of 180×300 mm2. While the profile of the electric field in a direction of microwave propagation showed existence of a standing wave, the plasma, such as emission intensity or ion current, had a flat distribution. The electric field and the plasma had flat distribution in a direction perpendicular to the microwave propagation. Besides, they were hardly dependent on chamber pressure. Therefore, a uniform plasma is stably produced in the present SWP applicator and can be produced over a larger area.
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52.50.Dg Plasma sources

X‐ray photoelectron spectroscopy study of surface layers on orthopaedic alloys. II. Co–Cr–Mo (ASTM F‐75) alloy

Gladius Lewis

J. Vac. Sci. Technol. A 11, 168 (1993); http://dx.doi.org/10.1116/1.578285 (7 pages) | Cited 2 times

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The differences and similarities between the compositional details of the layer formed on the surface of a Co–Cr–Mo alloy specimen when exposed for 1 h to laboratory air or wet steam are identified. An estimate of the thickness of each of these layers is also obtained.
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81.05.Bx Metals, semimetals, and alloys
68.35.Dv Composition, segregation; defects and impurities

Auger electron spectroscopy electron‐beam induced damage of a H2O‐covered Si(100) surface

L. Viscido and J. M. Heras

J. Vac. Sci. Technol. A 11, 175 (1993); http://dx.doi.org/10.1116/1.578697 (5 pages)

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The effect of 2‐keV electron‐beam irradiation on H2O adsorbed onto a Si(100) single crystal at 300 K was studied using Auger spectroscopy. The incident electron beam induces surface oxidation exclusively in the region irradiated as indicated by measurements of the lateral composition profile. Oxidation ceases when the broad SiLVV Auger peak extending from 74 to 83 eV is ≊5 times higher than the peak at 91 eV, a process which requires ≊80‐L H2O exposure (pH2O=1.3×10−7 mbar) using normal beam incidence. The oxygen atomic fraction at this point is ≊0.82. After 15 h at 300 K, the ratio of the normalized peak‐to‐peak signals at 78 and 511 eV is 1:1. A focused beam of 2‐keV 1‐mA emission (≊20‐μA sample current) in the absence of water is capable of destroying the oxide layer, practically recovering the clean surface after 1 h. Annealing at 800 K has little effect on the oxide. Depth profiling by Ar+ bombardment indicates that the thickness of the oxide film is ≊1.0 nm.
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81.65.-b Surface treatments
82.50.Kx Processes caused by X-rays or γ-rays
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.80.Fe Electron and positron radiation effects

X‐ray photoelectron spectroscopy analysis of the copper/arachidic acid organized molecular assembly interface: Charging phenomena

David E. King, A. W. Czanderna, and D. Spaulding

J. Vac. Sci. Technol. A 11, 180 (1993); http://dx.doi.org/10.1116/1.578698 (3 pages) | Cited 1 time

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Interactions of evaporated copper with the methyl terminated surfaces of self‐assembled monolayers of arachidic acid were studied with x‐ray photoelectron spectroscopy (XPS). The arachidic acid [CH3(CH2)19COOH] organized molecular assemblies (OMAs) were self‐assembled on native oxide grown on freshly prepared 200 nm thick aluminum films on single crystal silicon wafers. XPS spectra were acquired as a function of evaporated copper thickness. Charging shifts of up to 0.84 eV were observed for the C(1s), O(1s), and Cu(2p) photoemission lines during evaporation of up to 4.0 nm of copper. The thickness of the organized molecular assemblies (OMA) is approximately 2.7 nm on the native oxide surface, yielding a total thickness for the oxide/OMA stack of 6–7 nm.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Wear resistant sulfur films on hard ball bearing steel studied by Auger electron spectroscopy and sputter profiling, including factor analysis

C. Jansson, G. T. Nielsen, J. Jakobsen, and P. Morgen

J. Vac. Sci. Technol. A 11, 183 (1993); http://dx.doi.org/10.1116/1.578699 (12 pages) | Cited 1 time

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Tribological procedures with hard SAEb) 52100 steel elements (hardness of 850 Vickers or above) leading to scoring resistant surfaces with sulfur films have been monitored with Auger electron spectroscopy and sputter profiling. For hard SAE 52100 steel with clean and dry surfaces, a criterion for scoring resistance is a static friction coefficient of 0.73–0.76. These surfaces are found to consist of an approximately 30‐Å‐thick upper region of oxide and sulfur. Sulfur was added to the lubricant in one of the steps of the procedure, after the end of which the majority of it (85%) was found to be bound to iron as in FeS. The formation of this sulphide film is the key to scoring resistance. For other, nonscoring resistant surfaces resulting from various unsuccessful procedures, only oxide films were formed, and no sulfur had been taken up by those surfaces. The sulfur film on a scoring resistant surface was shown to slow initial oxidation compared to a surface stripped of this film. Wear of hard steel surfaces in sliding contacts, without any sulfur in the surface region, was shown to occur through oxidation, with a release of oxide debris. Thus, oxides are not beneficial to scoring resistance.
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81.40.Pq Friction, lubrication, and wear

Nuclear magnetic resonance probe for low level hydrogen detection

D. H. Levy and K. K. Gleason

J. Vac. Sci. Technol. A 11, 195 (1993); http://dx.doi.org/10.1116/1.578701 (4 pages) | Cited 2 times

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The design for a nuclear magnetic resonance (NMR) probe capable of detecting hydrogen signals at levels of <5×1016 H/sample is presented. In order to reduce background signals, the design eliminates polymeric materials from the probe head area and allows for a dry nitrogen purge during experimental runs to avoid signals due to ambient moisture. In addition, a metal cleaning process is employed that removes 1H NMR detectable contaminants from copper components. Use of this NMR probe for thin solid films and other low hydrogen content materials is demonstrated. The probe holds these samples without a NMR sample tube, further eliminating background hydrogen signals. In addition, a calibration curve for low hydrogen content standards demonstrates that NMR signal response is indeed linear at low hydrogen concentrations, leading to accurate quantification of hydrogen.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Study of band gap and band levels of Cu–In–Se–Te thin films compounds

R. Díaz and M. León

J. Vac. Sci. Technol. A 11, 199 (1993); http://dx.doi.org/10.1116/1.578702 (6 pages) | Cited 2 times

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The first direct gap of Cu–In–Se–Te thin films grown by triode sputtering has been determined, showing values in the 0.76–1.42 eV range. The spread of values is explained assuming that the Cu/In atomic ratio of sample composition affects significantly the conduction band minimum whereas the valence band maximum is concerned by the Cu/(Se+Te) atomic ratio. In any case, the variation observed in the energy gap is mainly due to changes in the Cu/In atomic ratio.
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73.20.At Surface states, band structure, electron density of states

Studies of hydrogen desorption from cobalt surfaces

A. L. Cabrera

J. Vac. Sci. Technol. A 11, 205 (1993); http://dx.doi.org/10.1116/1.578704 (4 pages) | Cited 2 times

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The adsorption of hydrogen at room temperature on cobalt samples was studied with thermal desorption spectroscopy. Desorption from cobalt foil was studied using a mass spectrometic method in an ultra high vacuum system, while desorption from cobalt powder was studied in a microreactor system using a thermal conductivity detector. Two hydrogen desorption peaks are observed in both cases. These states correspond to the β1 and β2 states observed in most transition metals. An activation energy of 4–5 kcal/mol is obtained for the β1 state while an energy of 12–19 kcal/mol for the β2 state. These two states are observed for complete hydrogen coverage on polycrystalline samples, independently of surface orientation. The hydrogen desorption peaks can be fitted with near Gaussian curves which facilitates the analysis of the curves to obtain activation energies. A tentative explanation of the appearance of these two states is offered based on surface atomic morphology.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Application of luminescence techniques to probe surface–adsorbate interactions on oxide single crystals

H. Idriss, R. M. Andrews, and M. A. Barteau

J. Vac. Sci. Technol. A 11, 209 (1993); http://dx.doi.org/10.1116/1.578705 (10 pages)

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Luminescence from semiconducting metal–oxide single crystals can provide important insights into the nature of the surface–adsorbate bond. This study examines cathodoluminescence from a zinc oxide single crystal and changes induced by adsorption and reaction of various oxygen‐containing reagents on the (0001) Zn‐polar plane. The electron gun on board the UHV surface analysis instrument was used to excite luminescence from the solid; emission spectra were measured with an optical system external to the chamber. Both the band gap emission (in the UV region at 380 nm) and the subband gap emission (in the visible region at 500 nm) characteristic of zinc oxide were monitored in cathodoluminescence from the single crystal. Adsorption at room temperature of methanol, formic acid, acetone, 2‐propanol, methyl formate and benzaldehyde on the ZnO(0001) surface produced an irreversible increase of the band gap emission in each case. The UV intensity returned to its original level (i.e., to that of clean zinc oxide before adsorption) after annealing the surface to temperatures high enough to desorb and decompose organic adsorbates (700–800 K). The increase in intensity of the UV emission was proportional to the amount of adsorbate on the surface, demonstrated by the correlation of the integrated C(1s) peak intensity of the adsorbate in x‐ray photoelectron spectroscopy with the change in the luminescence intensity. The luminescence peak intensity normalized by the surface coverage, referred to as the ‘‘specific luminescence,’’ decreased with increasing ionization potential of the reactant adsorbed. Failure to normalize the change in luminescence intensity for varying saturation coverages of different adsorbates produced the opposite trend. These results demonstrate that it is essential to calibrate surface coverage independently in order to relate the perturbation of the solid to the electronic properties of the adsorbate. This work demonstrates the application of luminescence to probe reactions on oxide surfaces, it illustrates the advantages of typical UHV surface analysis instruments for such experiments, and it considers the potential for quantitative determination of the extent of charge transfer between adsorbate and surface.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Sq Composite materials
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Infrared study of electron‐beam‐induced reactions in Langmuir–Blodgett films of stearic acid

Fumiko Yano, Veronica A. Burrows, Michael N. Kozicki, and Joseph Ryan

J. Vac. Sci. Technol. A 11, 219 (1993); http://dx.doi.org/10.1116/1.578706 (5 pages) | Cited 2 times

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To investigate the mechanisms of carbon enhanced vapor etching of silicon oxide, electron‐beam‐induced reactions in stearic acid Langmuir–Blodgett (LB) films were studied as a model system. Stearic acid LB films were deposited on silicon, and characterized using multiple internal reflection infrared spectroscopy. Spectra of these films exposed to an electron beam show changes in both peak shape and intensity. The changes are shown to result from both electron‐beam‐induced evaporation, and from carbon–carbon bond dissociation within the films.
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68.18.-g Langmuir-Blodgett films on liquids
82.50.Kx Processes caused by X-rays or γ-rays
68.55.-a Thin film structure and morphology
78.66.Qn Polymers; organic compounds

Point defect structures and energetics in Si using an empirical potential

P. J. Ungar, T. Takai, T. Halicioglu, and W. A. Tiller

J. Vac. Sci. Technol. A 11, 224 (1993); http://dx.doi.org/10.1116/1.578707 (7 pages) | Cited 2 times

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Statics calculations on silicon using the Tersoff 2 and Tersoff 3 potential energy functions are presented. We have evaluated the following at 0 K: (1) neutral monovacancy and divacancy formation and migration energies; (2) neutral bond‐centered, site sharing, tetrahedral, and hexagonal self‐interstitial formation and migration energies; and (3) the variation of these energies with distance from a bulk site of Frenkel defect formation and from [100] and [111] surfaces. The structural variations around these defects are also determined and discussed.
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61.72.J- Point defects and defect clusters
61.72.Bb Theories and models of crystal defects
66.30.Lw Diffusion of other defects

Computer solution to chamber‐gas fractionation during pumpdown

Donald Santeler and David Warren

J. Vac. Sci. Technol. A 11, 231 (1993); http://dx.doi.org/10.1116/1.578708 (9 pages)

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The evacuation process of a gas mixture in the molecular flow range is characterized by the fact that each gas type is separately pumped at its own respective pumping speed. Since the pumping speeds for most high‐vacuum pumps depend on the individual gas type and, further, since the molecular gas‐flow conductance is dependent on the inverse square‐root‐of‐mass behavior, gas fractionation occurs. This merely means that the gases which have higher pumping speed are removed faster leaving the gases with lower speed as the predominant residuals. By far, the most common occurrence of gas fractionation is during the evacuation of almost every high‐vacuum system. While gas fractionation is most predominant in the molecular flow range, it also occurs in the transition range where the gas‐flow behavior is mathematically more complex. The net result of gas fractionation is that the relative composition of the residual gas in the vacuum system steadily changes with time during pumpdown. Since the mathematical aspects of gas fractionation are well established, it seems reasonable that this phenomenon should be simulated in modern computer programs which otherwise simulate the normal vacuum system behavior of gas flow as a function of pressure and of system pressure as a function of time. This article discusses some of the complex interacting problems as well as a final solution which was applied to a specific commercial vacuum‐system‐design computer program, VSD‐II.
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07.30.Bx Degasification, residual gas
47.45.Dt Free molecular flows

Ion deflector of an ionization gauge for extreme high vacuum

A. Otuka and C. Oshima

J. Vac. Sci. Technol. A 11, 240 (1993); http://dx.doi.org/10.1116/1.578709 (5 pages) | Cited 8 times

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An ion deflector of an ionization pressure gauge for an extreme high vacuum use has been developed. On the basis of the calculated ion trajectories, the optimum deflection angles of the electrostatic cylindrical deflector have been determined versus the electrode gap: an excellent focusing of ion beam has been established at the optimum angles. This is important in order to use the channeltron and to remove the electron stimulated desorption (ESD) noise from the signals. We have realized a high efficiency of ion collection together with a large reduction of the two noises of soft x‐ray photoemission current and ESD ions by using the ion deflector.
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07.30.Dz Vacuum gauges

New flow behavior of gases and vapors in vacuum at very low flow rates

N. Venkataramani, F. Ghezzi, and G. Bonizzoni

J. Vac. Sci. Technol. A 11, 245 (1993); http://dx.doi.org/10.1116/1.578710 (10 pages) | Cited 2 times

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An investigation of flow of gases and vapors in vacuum through a path of very small cross‐sectional area, namely that of a high vacuum gas leak valve, reveals the existence of a new flow behavior which is well behaved. The characteristics are different from that of the molecular flow or that of the sonic flow through a small aperture. The unambiguous nature of the flow has been observed by three independent flow measurement techniques. The conductance is found to decrease with the pressure upstream and depends on the geometry and specie. The effect of the residence time of the gas molecules during the collisions with the wall of the conducting path has been attributed as a possible mechanism to explain the observed flow phenomenon. The flow behavior has also been studied for two isotopic water vapors. Based on the defined characteristics of the flow, an application technique is proposed for finding the partial pressures of the component vapor and gases in a low‐vacuum system by making the measurements in a coupled high vacuum system using a quadrupole mass analyzer. The applicability and sensitivity of the technique are demonstrated by an example measurement of the compositions of hydrogen and oxygen gas mixture.
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47.45.-n Rarefied gas dynamics
07.30.Bx Degasification, residual gas

Differential pumping of Ar/H2 gas mixtures and carbon film deposition

Kevin R. Coffey and Timothy M. Reith

J. Vac. Sci. Technol. A 11, 255 (1993); http://dx.doi.org/10.1116/1.578711 (6 pages)

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The deposition of hydrogenated carbon thin films is currently of technological interest to thin film disk manufacturing. The use of Ar/H2 gas mixtures to deposit these films is complicated by the differences in molecular flow properties of Ar and H2. As a result, the hydrogen concentration in the deposition chamber is not necessarily equal to that of the supply gas. The difference can be significant and is variable. The variation is due to vacuum pumping system design and adjustment, as well as carbon film deposition conditions. The need to control this variation is based upon the desire to provide hydrogenated carbon films with controlled composition.
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07.30.Cy Vacuum pumps
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Accuracy and applicability of the spinning rotor gauge to calibration in gas mixture environments

L. D. Hinkle and R. P. Jacobs

J. Vac. Sci. Technol. A 11, 261 (1993); http://dx.doi.org/10.1116/1.578713 (3 pages) | Cited 1 time

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The spinning rotor gas friction gauge (SRG) is being used increasingly for measurement and calibration of gauges in cases where a single gas type environment is not achievable. This may involve gas mixtures composed of molecules with differing mass values and surface interaction characteristics. Since the molecular momentum transfer and hence rate of rotational decay of the spinning rotor depend on molecular mass and accommodation coefficient, the calibration of the pressure indication must reflect the gas mixture ratio. The theoretical expression for the calibration factor is derived and compared with experimental data in the molecular flow regime. Agreement to within 5% is typical with inert gas mixtures. The proper application of this method allows the SRG to accurately calibrate other high vacuum gauges for use with known gas mixtures encountered in processing conditions.
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07.30.Dz Vacuum gauges

Flux measurement of a hyperthermal atomic oxygen beam

Mark R. Davidson, Gar B. Hoflund, and R. A. Outlaw

J. Vac. Sci. Technol. A 11, 264 (1993); http://dx.doi.org/10.1116/1.578714 (3 pages) | Cited 3 times

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A method has been developed and is described for measuring the flux of a beam of hyperthermal oxygen atoms using a quadrupole mass spectrometer. The accuracy of this method has been assessed by adsorbing the O atom flux on a Au surface for a specified period of time and quantifying the adsorbed amount using ion scattering spectroscopy and by estimating the oxygen‐atom flux from the electron stimulated desorption parameters used to produce the oxygen‐atom beam.
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41.85.Ew Particle beam profile, beam intensity
07.77.-n Atomic, molecular, and charged-particle sources and detectors
07.75.+h Mass spectrometers

New rotating target holder for laser ablation and ion beam sputter deposition of multicomponent and multilayered thin films

O. Auciello, J. Emerick, J. Duarte, and A. Illingworth

J. Vac. Sci. Technol. A 11, 267 (1993); http://dx.doi.org/10.1116/1.578715 (4 pages) | Cited 4 times

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A versatile ultrahigh vacuum rotating target holder has been designed and constructed for use in ion beam sputter and laser ablation deposition systems for producing multicomponent and/or multilayered thin films. The device features a capability for rotating the targets continuously during exposure to the beams to minimize the development of an undesirable surface topography that otherwise would occur if the targets were still during irradiation. In addition, each individual target holder can be tilted at a predetermined angle. The combined tilting and rotation produces a wobbling movement of the target surface that can be used advantageously to achieve a more uniform distribution of the materials ejected from the targets, which in turn can result in better composition and thickness uniformity of thin films over large area substrates. The device can be baked up to 150 °C depending on the choice of driving motor.
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81.15.Cd Deposition by sputtering
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Fg Pulsed laser ablation deposition
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Erratum: ‘‘Optical emission investigation of the plasma enhanced chemical vapor deposition of silicon oxide films’’ [J. Vac. Sci. Technol. A 10, 3395 (1992)]

A. Banerjee and T. DebRoy

J. Vac. Sci. Technol. A 11, 271 (1993); http://dx.doi.org/10.1116/1.578716 (1 page)

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An error in the reference list was detected. The correct version is as follows.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
99.10.Cd Errata
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