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Jul 2002

Volume 20, Issue 4, pp. 1171-1505

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Void formation during silicidation and its influence on the thermal stability of cobalt silicide

Nam-Sik Kim, Han-Seob Cha, Nag-Kyun Sung, Hyuk-Hyun Ryu, Ki-Seog Youn, and Won-Gyu Lee

J. Vac. Sci. Technol. A 20, 1171 (2002); http://dx.doi.org/10.1116/1.1477199 (6 pages) | Cited 2 times

Online Publication Date: 27 June 2002

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Void formation during silicidation and its influence on the thermal stability of CoSi2 on the poly-Si were investigated. Visible voids were found at the interface of CoSi2/poly-Si on the BF2 doped poly-Si but not on the boron doped one. Void formation during silicidation could be suppressed effectively by two methods: preventing oxidation of poly-Si during dopant activation annealing or removing surface SiOx(Fy) compounds sufficiently in dilute HF before cobalt deposition. It was found that the thermal stability of CoSi2 on the BF2 doped poly-Si with the interface voids was much better than that on the boron doped one or BF2 doped one, without the interface voids. It is verified that interface void formation during silicidation improves the thermal stability of CoSi2 by suppressing the grain grooving from the interface due to the increase of interface energy. © 2002 American Vacuum Society.
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81.05.Cy Elemental semiconductors
68.35.Ct Interface structure and roughness
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.60.Dv Thermal stability; thermal effects
81.65.Mq Oxidation

Model for a multiple-step deep Si etch process

Shahid Rauf, William J. Dauksher, Stephen B. Clemens, and Kenneth H. Smith

J. Vac. Sci. Technol. A 20, 1177 (2002); http://dx.doi.org/10.1116/1.1477418 (14 pages) | Cited 17 times

Online Publication Date: 27 June 2002

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A multiple-step deep Si etch process involving separate etching and polymerization steps is often employed for fabrication of microelectromechanical systems, microfluidics devices, and other assorted deep structures in Si. An integrated plasma equipment-feature evolution model for this multiple-step deep Si etch process is described in this article. In the two-dimensional plasma equipment model, the etching (SF6/O2) and polymerization [octafluorocyclobutane(c-C4F8)] chemistries are separately simulated assuming steady-state conditions. The outputs of the equipment simulations are combined in a string-based feature profile evolution model to simulate the multiple-step deep Si etch process. In the plasma equipment models, detailed gas phase plasma chemistries including electron impact processes, ion–molecule reactions, and neutral chemistry have been considered for both the etching and polymerization gas mixtures. The plasma–surface interaction mechanisms in the feature profile evolution model are based on qualitative information available in literature and the correlation of modeling results with experimental data. Under the relevant operating conditions, F is assumed to be the primary Si etchant, film deposition in c-C4F8 is due to sticking of C, CF2, and C2F4 under ion bombardment, and the polymer is etched by energetic ions through physical sputtering. It is demonstrated that predictions of the resulting model are in close agreement with experiments. The validated model is used to understand the dynamics of the multiple-step deep Si etch process and how etching characteristics can be controlled using a variety of process parameters. Etching characteristics have been found to be quite sensitive to gas pressure, coil power, bias power, and relative step time during both etching and polymerization processes. The Si etch rate and feature sidewall angle are coupled to each other over a wide range of operating conditions. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.35.-x Polymers: properties; reactions; polymerization
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.20.Wk Machining, milling
52.65.-y Plasma simulation
82.20.Pm Rate constants, reaction cross sections, and activation energies

Bi epitaxy on polar InSb(111)A/B faces

Sunglae Cho, Young-Ho Um, Yunki Kim, George K. L. Wong, J. B. Ketterson, and Jung-Il Hong

J. Vac. Sci. Technol. A 20, 1191 (2002); http://dx.doi.org/10.1116/1.1479735 (4 pages) | Cited 1 time

Online Publication Date: 27 June 2002

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Bi thin films have been grown on InSb(111)A/B substrates using molecular beam epitaxy. We have observed different Bi atomic surface structures on polar InSb(111)A and B faces as well as thickness dependent surface structures on the A face. Bi deposited on InSb(111)B shows a (1×1) surface structure, i.e., no surface reconstruction. However, Bi on InSb(111)A shows a (2×2) structure for thicknesses less than 16 Å, thereafter changing to a (1×1) structure. On both surfaces, Bi grows in a layer-by-layer growth mode with high crystallinity and sharp interfaces. © 2002 American Vacuum Society.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.40.Ns Metal-nonmetal contacts

Maintaining reproducible plasma reactor wall conditions: SF6 plasma cleaning of films deposited on chamber walls during Cl2/O2 plasma etching of Si

Saurabh J. Ullal, Harmeet Singh, John Daugherty, Vahid Vahedi, and Eray S. Aydil

J. Vac. Sci. Technol. A 20, 1195 (2002); http://dx.doi.org/10.1116/1.1479733 (7 pages) | Cited 34 times

Online Publication Date: 27 June 2002

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Silicon oxychloride films deposited on plasma etching reactor walls during the Cl2/O2 plasma etching of Si must be removed to return the reactor to a reproducible state prior to etching the next wafer. Using multiple surface and plasma diagnostics, we have investigated the removal of this silicon oxychloride film using an SF6 plasma. In particular, a diagnostic technique based on the principles of multiple total internal reflection Fourier transform infrared spectroscopy was used to monitor the films that formed on the reactor walls. The silicon oxychloride film etching proceeds by incorporation of F, which also abstracts and replaces the Cl atoms in the film. If the SF6 plasma is not maintained for a sufficiently long period to remove all the deposits, the F incorporated into the film leaches out into the gas phase during the subsequent etch processes. This residual F can have undesirable effects on the etching performance and the wafer-to-wafer reproducibility. The removal of the silicon oxychloride film from the reactor walls is inherently nonuniform and the end of the cleaning can be detected most easily by monitoring reactor averaged F and SiF emissions. © 2002 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning
52.40.Hf Plasma-material interactions; boundary layer effects
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Calibration stability of hot cathode ionization gauges: A discussion of the importance of electron path length and gauge constant

R. N. Peacock

J. Vac. Sci. Technol. A 20, 1202 (2002); http://dx.doi.org/10.1116/1.1479358 (3 pages) | Cited 1 time

Online Publication Date: 27 June 2002

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The ion current, i+, in an ionization gauge is given by the equation i+=Ki−P where K is a gas dependent gauge constant, i− is the electron current, and P is the pressure. Values of K for nitrogen for gauges designed for use at ultrahigh vacuum and extreme high vacuum range from 10/Torr to 106/Torr. It is important to know whether calibration stability is sacrificed when K, and the electron path length are large. Using a simple model, the electron path length is estimated as a function of the probability, β, that an electron will make another pass through the ionizing region. An equation is obtained for K as a function of β. The fractional change in K, ΔK/K, is zero for those gauges where the electrons make a single pass, but is increasingly larger for higher sensitivity gauges with greater probabilities of multiple passes. As an example, assume that the probability of the next pass changes by 1%, then the change in sensitivity is 1.5% for a B-A with K=25/Torr, and 9% for a gauge with K=102/Torr. © 2002 American Vacuum Society.
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07.30.Dz Vacuum gauges
06.20.F- Units and standards

Atomic force microscopy observation of TiO2 films deposited by dc reactive sputtering

T. Takahashi, H. Nakabayashi, T. Terasawa, and K. Masugata

J. Vac. Sci. Technol. A 20, 1205 (2002); http://dx.doi.org/10.1116/1.1479356 (5 pages) | Cited 6 times

Online Publication Date: 27 June 2002

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A bombardment of energetic particles such as secondary electrons and recoiled ions ejected from the target plane is a very useful technique for modifying the structure of the film in reactive sputtering. It leads to interesting effects such as enhancement of reactivity, adatom mobility, and atomic peening. Therefore, the state on the surface of the as-deposited film may significantly depend on the bombardment condition. So, in this study, the relationship between the bombardment condition and the surface morphology of TiO2 films has been investigated in detail. TiO2 films with a thickness of about 0.8–2.3 μm were deposited by dc reactive sputtering on glass-slide substrates. The surface roughness of films was measured with atomic-force microscopy. The roughness parameter Ra on the surface of TiO2 films depended on the energy and the number of bombarding particles. After increasing the energy and the number of bombarding particles, Ra increased from 10 to 77 nm. Consequently, it was found that the surface morphology of TiO2 films strongly affected the plasma exposure to the growing film. © 2002 American Vacuum Society.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.37.Ps Atomic force microscopy (AFM)
79.20.Kz Other electron-impact emission phenomena
61.80.Fe Electron and positron radiation effects

Influence of nitrogen and temperature on the plasma deposition of fluorinated amorphous carbon films

L. Valentini, J. M. Kenny, R. M. Montereali, L. Lozzi, and S. Santucci

J. Vac. Sci. Technol. A 20, 1210 (2002); http://dx.doi.org/10.1116/1.1479359 (6 pages) | Cited 1 time

Online Publication Date: 27 June 2002

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In this work, the effects of nitrogen addition on the properties of a-C:H:F films produced by rf plasma enhanced chemical vapor deposition at different temperatures are reported. The structural and optical properties were investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, ultraviolet-visible transmittance and ellipsometry measurements. The dependence of both fluorine and nitrogen incorporation in the carbon matrix on the deposition temperature was analyzed. The main effect of progressive nitrogen incorporation is a decrease of transmittance and optical band gap of the samples grown at room temperature and at 400 °C. Raman spectra evidence that for films deposited at 400 °C a sudden loss of sp3 carbon bonding occurs. In particular, at fixed plasma composition, the decrease of the optical band gap is interpreted as a clustering of the existing sp2 carbon sites. Ellipsometry characterization indicates that nitrogen incorporation for the samples deposited at room temperature induces an increase of the refractive index while films deposited at 400 °C are characterized by a reduction of the refractive index; this has been correlated to changes in the graphitic cluster size of the network. In particular, the increase in the deposition temperature produces an increase in the size of the graphitic clusters. © 2002 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
81.05.U- Carbon/carbon-based materials
68.55.A- Nucleation and growth
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
79.60.Dp Adsorbed layers and thin films
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.40.Pg Disordered solids
61.43.Er Other amorphous solids
78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.23.Cq Amorphous semiconductors, metallic glasses, glasses

Molecular drag model based on differential reduction of the Kruger–Shapiro equations

J. C. Helmer and G. Levi

J. Vac. Sci. Technol. A 20, 1216 (2002); http://dx.doi.org/10.1116/1.1479734 (6 pages) | Cited 1 time

Online Publication Date: 27 June 2002

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The history of the method of differential probability in molecular flow is reviewed, beginning with the little known derivation by D. Santeler (5th Annual Symposium on Space Environmental Simulation, Arnold Air Force Station, TN, May, 1964), based on the equation of C. W. Oatley [Br. J. Appl. Phys. 8, 15 (1957)]. This method contains the aperture correction within the theory, without phenomenological assumptions. A new equation of this type, for molecular pumping, is derived by differential reduction of the Kruger–Shapiro equations. A simple solution of the differential equations yields results of good accuracy for engineering use. The physical characteristics of molecular pumping are clarified by describing the pressure distribution within the pumping tube as if it were a conductance. By this method the calculated performance of a model pump is shown to be in satisfactory agreement with a Clausing-type solution from a previous publication. © 2002 American Vacuum Society.
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47.45.Dt Free molecular flows
07.30.Bx Degasification, residual gas

Investigation and reduction of spurious peaks caused by electron-stimulated desorption and outgassing by means of a grid heating method in a hot-cathode quadrupole residual gas analyzer

Fumio Watanabe

J. Vac. Sci. Technol. A 20, 1222 (2002); http://dx.doi.org/10.1116/1.1479736 (8 pages) | Cited 3 times

Online Publication Date: 27 June 2002

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In the year 2001, two issues remain for extreme high vacuum (XHV) pressure measurements with hot-cathode ionization gauges: measurement limits caused by electron-stimulated desorption (ESD) and outgassing. The limit caused by ESD is significantly clarified and at least partially solved by means of a grid heating method in a residual gas analyzer. After system bakeout and at 10−9 Pa, when the surface of a platinum alloy grid remains contaminated with F and Cl atoms and CO molecules, the mass spectrum is dominated by spurious peaks (which set the measurement limit for a total pressure gauge) caused by ESD species of F, Cl, and O, with a yield of 10−11 (species/electron, with neutral/ion ≅0.3) and by CO molecule ESD, with a yield of 10−11 (species/electron, with CO neutral/O ion ≅18). In this condition, a spurious H peak caused by hydrogen ESD is still low. However, once the grid surface is thoroughly cleaned at over 900 °C by ohmic heating or electron bombardment, the major ESD species observed for both neutrals and ions dramatically changes to mainly a spurious H peak with a yield of 10−11 (species/electron, with neutral/ion ≅2). When the operational grid temperature is then increased to 500 °C, the spurious H peak is decreased by over 3 orders of magnitude and the spectrum becomes mainly H2 molecules, reflecting the true pressure of the system; i.e., the relative error for the pressure is reduced to 8% from 614%. The lower limit caused by outgassing in these instruments is due to the grid bulk content of hydrogen. Finding a lower-hydrogen solubility material for the grid may become the last work required for lower-limit XHV gauge development. In order to decrease the limits caused by ESD and outgassing in a hot-cathode gauge, employing ion energy filters and cold-cathode field emitters is unnecessary. © 2002 American Vacuum Society.
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07.30.Bx Degasification, residual gas
07.30.Dz Vacuum gauges
68.43.Rs Electron stimulated desorption

Investigation of surface oxides on aluminum alloys by valence band photoemission

Gregory D. Claycomb and Peter M. A. Sherwood

J. Vac. Sci. Technol. A 20, 1230 (2002); http://dx.doi.org/10.1116/1.1479357 (7 pages) | Cited 2 times

Online Publication Date: 27 June 2002

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Core level and valence band x-ray photoelectron spectroscopy are used to study the chemical composition of the surface films on aluminum alloys. Certain alloying elements may preferentially migrate to the surface of an alloy, thereby altering the composition and consequently the chemistry of the surface. The behavior of a 6061 aluminum alloy is compared with that of pure aluminum. It is shown that the type of magnesium film formed at the alloy surface can be determined by comparing the valence band spectra of the aluminum alloy surface with that of known magnesium and aluminum compounds. The experimental valence band spectra of these compounds are supported by spectra generated from band structure calculations. The effect of boiling water on the surface film is discussed, with significant differences in surface chemistry being seen for the metal and the alloy. © 2002 American Vacuum Society.
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81.65.Mq Oxidation
68.35.Dv Composition, segregation; defects and impurities
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Jv Interfaces; heterostructures; nanostructures

Direct measurement of residual gas effect on the sensitivity in TAMA300

R. Takahashi, Y. Saito, M. Fukushima, M. Ando, K. Arai, D. Tatsumi, G. Heinzel, S. Kawamura, T. Yamazaki, and S. Moriwaki

J. Vac. Sci. Technol. A 20, 1237 (2002); http://dx.doi.org/10.1116/1.1479360 (5 pages) | Cited 3 times

Online Publication Date: 27 June 2002

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A laser interferometer gravitational wave detector requires an ultrahigh vacuum in the tubes in which the laser beams pass. TAMA300, involves two 300-m vacuum tubes, and is kept at 2×10−6 Pa of vacuum pressure so as to reduce scattering effects due to residual-gas molecules. The sensitivity attained so far is 2×10−18 m/math around 1 kHz. By introducing a Xe gas into the entire system of TAMA300, we directly observed the residual-gas effect on the sensitivity. It was found that Xe-gas pressure of 0.03 Pa induces an increase in the mirror displacement noise of 3×10−18 m/math. This noise level is consistent with a calculated optical fluctuation of the laser beam due to residual-gas scattering. © 2002 American Vacuum Society.
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04.80.Nn Gravitational wave detectors and experiments
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
07.30.Bx Degasification, residual gas
07.60.Ly Interferometers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Effects of argon addition on a-CNx film deposition by hot carbon filament chemical vapor deposition

Yoshihisa Watanabe, Masami Aono, Ayumi Yamazaki, Nobuaki Kitazawa, and Yoshikazu Nakamura

J. Vac. Sci. Technol. A 20, 1242 (2002); http://dx.doi.org/10.1116/1.1481757 (5 pages) | Cited 1 time

Online Publication Date: 27 June 2002

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Using a carbon filament which supplies carbon and heat, amorphous carbon nitride (a-CNx) films were prepared on Si (100) substrates by hot filament chemical vapor deposition. Deposition was performed in a low-pressure atmosphere of pure nitrogen and a gas mixture of nitrogen and argon. Effects of argon additions to the nitrogen atmosphere on the film microstructure and interface composition between the film and substrate were studied by field-emission scanning electron microscopy (FESEM) and x-ray photoelectron spectroscopy (XPS). FESEM observations reveal that the film prepared in a pure nitrogen atmosphere has uniform nucleation and a densely packed columnar pieces structure. The film prepared in the nitrogen and argon gas mixture exhibits preferential nucleation and a tapered structure with macroscopic voids. Depth analyses using XPS reveal that the film prepared in pure nitrogen possesses a broad interface, which includes silicon carbide as well as a-CNx, whereas a sharp interface is discerned in the film prepared in the mixed nitrogen and argon gas. We observed that silicon carbide formation is suppressed by an argon addition to the nitrogen atmosphere during deposition. © 2002 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.43.Er Other amorphous solids
68.55.-a Thin film structure and morphology
81.05.U- Carbon/carbon-based materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.55.A- Nucleation and growth

Control of secondary phase segregations during CuGaSe2 thin-film growth

M. R. Balboul, U. Rau, G. Bilger, M. Schmidt, H. W. Schock, and J. H. Werner

J. Vac. Sci. Technol. A 20, 1247 (2002); http://dx.doi.org/10.1116/1.1481039 (7 pages) | Cited 2 times

Online Publication Date: 27 June 2002

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The influence of the Se evaporation rate during deposition of CuGaSe2 thin films by coevaporation of the elements on Na-containing glass substrates is investigated. A high Se rate is found to avoid the segregation of a Na-containing secondary phase which, in the case of too low Se rates, is deleterious for the performance of the CuGaSe2 films. In addition, the article proposes a model for the phase segregation under low-Se conditions invoking sodium monoselenide as a precursor for the secondary phase. The segregation of the Na-containing compound in CuGaSe2 is further assisted by Ga diffusion from the CuGaSe2 film into the glass substrate. The present results also show that ionic exchange between Na from the glass and Ga from the absorber is active during the growth of Cu(In,Ga)Se2 alloys on Na-containing glass. © 2002 American Vacuum Society.
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68.60.Wm Other nonelectronic physical properties

Plasma etching of SiC surface using NF3

A. Tasaka, K. Takahashi, K. Tanaka, K. Shimizu, K. Mori, S. Tada, W. Shimizu, T. Abe, M. Inaba, Z. Ogumi, and T. Tojo

J. Vac. Sci. Technol. A 20, 1254 (2002); http://dx.doi.org/10.1116/1.1481044 (7 pages) | Cited 10 times

Online Publication Date: 27 June 2002

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NF3 was applied in the reactive ion etching of SiC. The effects of rf power and NF3 pressure on the etching rate and the surface morphology were investigated by means of scanning electron microscopy and atomic force microscopy. A procedure for getting the smooth and residue-free etched surface of SiC with a high etching rate of 87 nm/min was obtained under the conditions such as rf power of 100 W and NF3 pressure ranging from 0.5 to 1 Pa. A rough surface with spikes was obtained under the NF3 pressures higher than 3 Pa. It was found that the repetitive alternating treatment for the spike-formed and rough surface with the down flow etching using NF3 and Ar plasma sputtering enables us to obtain the smooth surface within the scale of ∼300 nm. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Hd Other semiconductors
68.37.Ps Atomic force microscopy (AFM)

Dynamics of the ion beam induced nitridation of silicon

Prakash N. K. Deenapanray

J. Vac. Sci. Technol. A 20, 1261 (2002); http://dx.doi.org/10.1116/1.1481045 (9 pages) | Cited 3 times

Online Publication Date: 27 June 2002

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High-resolution Rutherford backscattering and channeling has been used to study the energy and angular dependence of the ion beam induced nitridation of Si in a secondary ion mass spectrometry system. The nitridation of Si is characterized by two critical angles θc1 and θc2, corresponding to the formation of stoichiometric and overstoichiometric Si-nitride layers, respectively. For the N2+ bombardment in the 10 to 13.5 keV range, θc1 changes from 40° to 45°, while θc2 changes from 28° to 30°. Further, strong oscillations in the secondary ion signal, observed for angles of incidence below θc2, are directly related to charging of the Si-nitride surface. We demonstrate that the response of the Si-nitride layer under ion bombardment during the transient stage of nitridation can be described by a second order differential equation. © 2002 American Vacuum Society.
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81.05.Cy Elemental semiconductors
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Influence of deposition temperature on the structure and internal stress of TiN films deposited by filtered cathodic vacuum arc

Y. H. Cheng, B. K Tay, and S. P. Lau

J. Vac. Sci. Technol. A 20, 1270 (2002); http://dx.doi.org/10.1116/1.1481043 (5 pages) | Cited 8 times

Online Publication Date: 27 June 2002

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TiN films were deposited by an off-plane double bend filtered cathodic vacuum arc technique. Atomic force microscopy and x-ray diffraction (XRD) were used to study the surface morphology and crystal structure of TiN films. Substrate bending methods were used to measure the internal stress. The influence of deposition temperature on the surface morphology, crystal structure, and internal stress were systematically studied. The surface roughness, grain size and the intensity of the XRD peak increase linearly with increasing deposition temperature. The crystallographic orientation develops from (111) preferred orientation to (200) preferred orientation as the deposition temperature is increased. The increase of deposition temperature from 50 to 450 °C results in a linear decrease of internal stress from 9.88 to 4.30 GPa. The enhancement of the mobility of atoms in the films and the variation of crystallographic orientation with increasing deposition temperature contribute to the decrease of internal stress in the films. © 2002 American Vacuum Society.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
68.37.Ps Atomic force microscopy (AFM)
61.05.cp X-ray diffraction

Effects of cross field diffusion in a low pressure high density oxygen/silane plasma

C. Charles

J. Vac. Sci. Technol. A 20, 1275 (2002); http://dx.doi.org/10.1116/1.1481042 (9 pages) | Cited 5 times

Online Publication Date: 27 June 2002

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A low pressure high density oxygen/silane radio frequency (13.56 MHz) plasma coupled in a helicon reactor used for silicon dioxide deposition is characterized by using an energy selective mass spectrometer situated at the wall of the processing chamber: measurements of positive and negative ion energy distribution functions and mass spectra (1⩽amu⩽150) are obtained for various flow-rate ratios (R=O2/SiH4=1 to 10 but constant total flow rate of 30 sccm), and for a constant radio frequency power and magnetic field of 800 W and 70 G, respectively. Plasma potentials between 35 (R=10) and 60 V (R=1) are measured depending on the silane and oxygen flows showing charging of the silica-covered diffusion chamber wall. The magnitude of the wall charging most likely depends on the effective capacitance formed by the silica layer (which results from months of deposition) and on the inbalance between the positively and negatively charged particles which impinge onto the sidewalls at the discharge initiation until equilibrium of fluxes is reached. This inbalance is a result of the magnetic field configuration generated by the four coils surrounding the reactor and of the subsequent cross-field diffusion of the positively and negatively charged particles to the sidewalls. Maximum wall charging is observed when the silane flow is maximum (R<2), a situation where polymerization is observed in the mass spectrum of the positive ions, and where a minimum density of negative ions (O−, OH−, and H−) are detected close to the walls. Although the polymerization appeared to be a primary candidate for the increase of the plasma potential to ∼60 V, its presence does not significantly change the total positive ion density at equilibrium but is accompanied by a dramatic decrease (two orders of magnitude for the O− ions) in the negative ion density close to the walls when R is increased from 1 to 10. The change in the degree of electronegativity close to the walls affects the global plasma equilibrium and appears as an indirect factor in the magnitude of the wall charging. © 2002 American Vacuum Society.
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52.80.Pi High-frequency and RF discharges
52.70.Nc Particle measurements

Atomistic feature scale modeling of the titanium ionized physical vapor deposition process

A. Kersch and U. Hansen

J. Vac. Sci. Technol. A 20, 1284 (2002); http://dx.doi.org/10.1116/1.1481041 (11 pages) | Cited 8 times

Online Publication Date: 27 June 2002

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We develop a fundamental model to simulate the ionized physical vapor deposition process of a titanium barrier into submicron features. Using molecular dynamics techniques we calculate for typical energies the energy and angular dependent reaction rates of Ti+ with Ti and Ar+ with Ti including the distribution of the etched away particles. The interaction potential is based on Ackland’s model [G. J. Ackland, Philos. Mag. A 66, 917 (1992)] and is extended for particles with a kinetic energy up to 150 eV. The reaction rates are implemented into a cellular automaton feature scale simulator modeling the thin film growth. The reactor and plasma sheath conditions are described in a simple model providing the energy and angular distribution for the feature scale simulator. The multiscale model is applied to barrier deposition into a high aspect ratio feature with different substrate bias conditions. The results show that the barrier growth at high energy is dominated by kinetic energy driven processes. © 2002 American Vacuum Society.
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81.05.Bx Metals, semimetals, and alloys
68.55.A- Nucleation and growth
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Properties and applications of cobalt-based material produced by electron-beam-induced deposition

Y. M. Lau, P. C. Chee, J. T. L. Thong, and V. Ng

J. Vac. Sci. Technol. A 20, 1295 (2002); http://dx.doi.org/10.1116/1.1481040 (8 pages) | Cited 66 times

Online Publication Date: 27 June 2002

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The deposition of cobalt-containing material from dicobalt octacarbonyl using a focused electron beam is reported. The material contains between 30% and 50% (atomic) cobalt, with the balance being carbon and oxygen, and comprises nanocrystalline metallic grains embedded in a carbonaceous matrix. Arches bridging two electrodes were fabricated to allow current–voltage (I–V) measurements to be conducted. The material resistivity decreases strongly with the deposition beam current, with values as low as 45 μΩ cm being attainable. Material growth by indirect irradiation is found to give rise to material of high resistivity and can result in highly resistive arches. At low temperatures, three distinctive conduction regimes are observed, with the I–V characteristics flattening out at the origin. At 20 K step-like features suggestive of Coulomb- blockade effects were observed. Magnetic force microscope (MFM) images of the material indicates that it is ferromagnetic in nature. The application of the technique and material to fabricate MFM tips is demonstrated. The use of selective material deposits as catalyst sites for the growth of carbon nanotubes is also demonstrated. © 2002 American Vacuum Society.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Numerical study of isotope separation phenomena of noble gases by dc discharge as rarefied gas dynamics

Mitsufumi Asami, Katsuhiro Kano, and Hiroshi Akatsuka

J. Vac. Sci. Technol. A 20, 1303 (2002); http://dx.doi.org/10.1116/1.1481046 (11 pages)

Online Publication Date: 27 June 2002

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A numerical simulation was undertaken on argon and krypton isotope separation in their dc arc discharges through a thin capillary. The mass transport phenomenon of neutral particles as well as of ions in the positive column was treated by direct simulation Monte Carlo method, whereas electrons were treated as background particles, and their behavior was assumed to be already given to evaluate the effects of electron collisions onto neutral particles. The numerical results agreed qualitatively with the isotope separation phenomena of argon and krypton dc discharges. The heavier isotopes were enriched into the region of the cathode, whereas the lighter ones into that of the anode. It was also found that the numerical results explained the pressure difference between the cathode and the anode observed experimentally. The characteristics of drift motion of ions also qualitatively agreed with existing experimental results. © 2002 American Vacuum Society.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
32.10.Bi Atomic masses, mass spectra, abundances, and isotopes
47.45.-n Rarefied gas dynamics

Characteristics of a direct metal ion beam deposition source

Daeil Kim and Steven Kim

J. Vac. Sci. Technol. A 20, 1314 (2002); http://dx.doi.org/10.1116/1.1482707 (6 pages) | Cited 3 times

Online Publication Date: 27 June 2002

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In this study, we examine the performance of a direct metal ion beam deposition (DMIBD) system which uses a Cs–mordenite pellet as the ion source. We describe design aspects of DMIBD and process parameters such as secondary ion yields, secondary ion energy distributions, secondary ion to atom arrival ratios and deposition rates for C, Al, Si, Ni, Cu, Ta, and W targets. During deposition, the secondary negative metal ion yield strongly depends on the primary Cs+ ion does and bombarding energy. Also, the deposition rate and ion to atom arrival ratios for various targets can be controlled by adjusting the primary Cs+ ion dose, Cs+ ion bombarding energy, and ion beam energy to fit the desired application. © 2002 American Vacuum Society.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
07.77.Ka Charged-particle beam sources and detectors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Characterization of TiAlN thin film annealed under O2 by in situ time of flight direct recoil spectroscopy/mass spectroscopy of recoiled ions and ex situ x-ray photoelectron spectroscopy

A. Tempez, A. Bensaoula, and A. Schultz

J. Vac. Sci. Technol. A 20, 1320 (2002); http://dx.doi.org/10.1116/1.1482711 (7 pages) | Cited 6 times

Online Publication Date: 27 June 2002

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The oxidation of an amorphous TiAlN coating has been studied by in situ direct recoil spectroscopy (DRS) and mass spectroscopy of recoiled ions (MSRI) and ex situ x-ray photoelectron spectroscopy (XPS). DRS and MSRI monitored the changes in surface composition as the sample was heated to 460 °C under an 18O2 pressure of 10−6 Torr. Angular resolved XPS data were acquired for thickness-dependence information. The initial surface was partially oxidized from air exposure. Both DRS and XPS showed the Al-rich near surface and the presence of N in the subsurface. As shown by DRS and MSRI, oxidation at elevated temperatures yielded surface nitrogen loss and Ti enrichment. XPS confirmed the preferential formation of TiO2 on the surface. This study also provides a comparison between the direct recoil (neutrals and ions) and the ionic recoil signals. In our conditions, the negative ionic fraction of all elements except H tracks their true surface content variations given by DRS. The results were compared with early work performed on identical samples. In this case the TiAlN film was oxidized with an O2 pressure in the mTorr range and the surface changes are followed in situ by positive MSRI and XPS. This experiment also indicates that Al and N are buried under TiO2 but from 600 °C. © 2002 American Vacuum Society.
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68.55.Nq Composition and phase identification
68.60.Wm Other nonelectronic physical properties
79.60.Dp Adsorbed layers and thin films
81.65.Mq Oxidation
61.43.-j Disordered solids
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.Dv Composition, segregation; defects and impurities
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.40.Gh Other heat and thermomechanical treatments

Substrate bias dependence of the structure and internal stress of TiN films deposited by the filtered cathodic vacuum arc

Y. H. Cheng, B. K. Tay, and S. P. Lau

J. Vac. Sci. Technol. A 20, 1327 (2002); http://dx.doi.org/10.1116/1.1482708 (5 pages) | Cited 8 times

Online Publication Date: 27 June 2002

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TiN films were deposited by an off-plane double bend filtered cathodic vacuum arc technique. Atomic force microscopy and x-ray diffraction were used to study the surface morphology and crystal structure. Substrate bending methods were used to determine the internal stress in the films. The influence of substrate bias on the structure and internal stress were systematically studied. As substrate bias is increased to −100 V, the surface roughness decreases to the minimum, the preferred orientation changes gradually from (200) to (111), and the internal stress increases greatly to the maximum. Further increase of substrate bias results in the drastic increase of surface roughness and the gradual decrease of internal stress. The preferred orientation changes gradually from (111) to (200). Except for the atomic peening, the change in the structure and preferred orientation also contributes to the variation of internal stress in the films with substrate bias. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)

Critical issues in the heteroepitaxial growth of alkaline-earth oxides on silicon

J. Lettieri, J. H. Haeni, and D. G. Schlom

J. Vac. Sci. Technol. A 20, 1332 (2002); http://dx.doi.org/10.1116/1.1482710 (9 pages) | Cited 57 times

Online Publication Date: 27 June 2002

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The critical aspects of the epitaxial growth of alkaline-earth oxides on silicon are described in detail. The step by step transition from the silicon to the alkaline-earth oxide as shown through reflection high energy electron diffraction is presented, with emphasis placed on the favorable interface stability, oxidation, structural, and strain considerations for each stage of the growth via molecular beam epitaxy. © 2002 American Vacuum Society.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Ct Interface structure and roughness

Method for seed and underlayer optimization of perpendicular magnetic recording media

Erik B. Svedberg, Rene Van de Veerdonk, Kent J. Howard, and Lynnette D. Madsen

J. Vac. Sci. Technol. A 20, 1341 (2002); http://dx.doi.org/10.1116/1.1482709 (6 pages) | Cited 2 times

Online Publication Date: 27 June 2002

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A set of seed and underlayers for thin film perpendicular recording media has been optimized using a technique involving simultaneous thickness and composition gradients on a single test wafer. Magnetron sputtering under ultrahigh vacuum conditions in Ar gas was used for the deposition of the layers. The structure being optimized consisted of a Ta seed layer, RuxCo1−x, Co63Cr37 underlayers, and a Co68Cr18Pt8B6 hard magnetic layer. One of the layers in the stack on a wafer has been deposited so that both a thickness variation and composition variation occurred. The method allows cross terms between thickness and the individual compositional terms to be investigated. Coercivity and squareness of the samples was measured by magneto-optical Kerr rotation. The results showed that for the range of thickness under investigation, the highest coercivity and squareness does not occur for the same set of conditions. Maximum squareness is reached without a radio frequency (rf) bias, while the coercivity increases further with the application of a −25 V rf bias. © 2002 American Vacuum Society.
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75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Vv High coercivity materials
81.15.Cd Deposition by sputtering
75.50.Ww Permanent magnets
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects

Reduction of metallic oxides by late Ar–H2–N2 postdischarges. I. Application to copper oxides

T. Belmonte, J. M. Thiébaut, H. Michel, R. P. Cardoso, and A. Maliska

J. Vac. Sci. Technol. A 20, 1347 (2002); http://dx.doi.org/10.1116/1.1484096 (6 pages) | Cited 5 times

Online Publication Date: 27 June 2002

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In this first part of a study dealing with the reduction of metallic oxides by Ar–N2–H2 postdischarges, copper oxide (CuO) is studied. The influence of the composition of both the gas mixture and the temperature on the reduction kinetics was measured, respectively, between 473 and 673 K. Measurements of the activation energies of the reduction reactions, together with optical emission spectroscopy in discharge and postdischarge, suggest that the reduction mechanisms of CuO is limited by the diffusion of hydrogen in copper below 573 K and by the dissociation of molecular hydrogen above. Atomic nitrogen can also react, but the reduction kinetics of metallic oxides by this specie is much slower than by H. © 2002 American Vacuum Society.
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81.65.Mq Oxidation
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Reduction of metallic oxides by late Ar–H2–N2 postdischarges. II. Applications to iron oxides

T. Belmonte, J. M. Thiébaut, H. Michel, R. P. Cardoso, and A. Maliska

J. Vac. Sci. Technol. A 20, 1353 (2002); http://dx.doi.org/10.1116/1.1484097 (5 pages) | Cited 3 times

Online Publication Date: 27 June 2002

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In this second part of a study dealing with the reduction of metallic oxide, iron oxide (Fe2O3) is treated by Ar–N2–H2 post discharges. The influence of the composition of both the gas mixture and the temperature on the reduction kinetics was measured between 783 and 868 K. If CuO is reduced to Cu (see Part I of the study), Fe2O3 is reduced to Fe2N1−x or Fe depending on the gas mixture composition. Measurements of the activation energies of the reduction reactions suggest that the reduction mechanisms of Fe2O3 are limited by the diffusion of oxygen in ε- Fe2N1−x. Similar conclusions to those drawn in the case of copper suggest that atomic nitrogen can reduce these oxides, but the reduction kinetics by this specie is much slower than by H. It is also confirmed that atomic hydrogen seems to affect the internal reaction at the interfaces of the sublayer oxides and modifies the activation energy of the growth processes. Finally, the reduction of titanium oxide (TiO2) at 873 K is not observed, and the reduction kinetics, and thus the treatment temperature, seems to depend on the metal–oxygen binding energy. © 2002 American Vacuum Society.
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81.65.Mq Oxidation
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Adsorption process of chlorine on Si(111)7×7 studied by surface differential reflectivity and second harmonic generation

M. Tanaka, T. Shirao, T. Sasaki, K. Shudo, H. Washio, and N. Kaneko

J. Vac. Sci. Technol. A 20, 1358 (2002); http://dx.doi.org/10.1116/1.1484098 (7 pages) | Cited 9 times

Online Publication Date: 27 June 2002

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The adsorption process of chlorine on Si(111)7×7 has been studied by means of real-time surface differential reflectance (SDR) spectroscopy and second harmonic generation. Time evolution of adsorption on adatom dangling bonds and breaking of adatom back bonds are obtained from SDR spectra and second harmonic intensity. The initial sticking probability on the dangling bonds and the initial breaking probability of the back bonds are determined by fitting the time evolution to the solutions of the rate equations for the adsorption of atoms without migration. Temperature dependence of these probabilities reveals that both the adsorption on adatom dangling bonds and breaking of adatom back bonds proceed without potential barriers, and that a metastable state exists in the breaking process of the back bonds. © 2002 American Vacuum Society.
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68.43.Mn Adsorption kinetics
78.68.+m Optical properties of surfaces
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Thin film transistors with anodic gate dielectrics and chemical bath deposited active layers

Feng Yuan Gan and Ishiang Shih

J. Vac. Sci. Technol. A 20, 1365 (2002); http://dx.doi.org/10.1116/1.1484095 (4 pages) | Cited 6 times

Online Publication Date: 27 June 2002

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Thin film transistors (TFTs) with an anodic dielectric layer and chemical bath deposited active layer have been fabricated on glass substrates. The effects of anodization conditions on the quality of the anodic dielectric were investigated by measuring the breakdown electric field and leakage current density of the metal–insulator–metal capacitors fabricated. Using the anodic gate dielectric, preliminary thin film transistors with CdS and CdSe films formed by a chemical bath deposition method were fabricated and evaluated. Results of electrical measurements carried out on the CdSe-TFTs with Al2O3 and Ta2O5 gate dielectrics showed field effect mobilities of 3.4 and 0.67 cm2/V s and threshold voltages of 3.2 and 8.2 V, respectively. Field effect mobilities of 0.2 and 2 cm2/V s and threshold voltages of 4.3 and 5.2 V were observed for CdS-TFTs, again with Al2O3 and Ta2O5 gate dielectrics. The mobilities obtained from the present TFTs fabricated on glass substrates are smaller than that on similar TFTs fabricated on thermally grown gate oxides on Si substrates in our previous work. © 2002 American Vacuum Society.
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85.30.Tv Field effect devices
77.55.-g Dielectric thin films
81.15.Pq Electrodeposition, electroplating

Study of the properties of thin films of silicon nitride and silicon oxide using effective medium theories

Redhouane Henda

J. Vac. Sci. Technol. A 20, 1369 (2002); http://dx.doi.org/10.1116/1.1486005 (5 pages) | Cited 2 times

Online Publication Date: 27 June 2002

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Effective medium theories (EMTs) find widespread applications in the general area of condensed matter. In this article, EMTs are used to investigate the properties of thin films of silicon nitride (SiNx) and silicon oxide (SiOx) produced by the low-pressure chemical vapor deposition technique. Experimental data on the technologically important properties, such as the optical constants and density, of these materials are compared with theoretical predictions using Clausius–Mossotti, Maxwell-Garnett, and Bruggemann equations. For both materials, the results show a good agreement between theoretical predictions as obtained from the solution of the Bruggemann equation and the experimental data up to the percolation threshold. The experimental results agree fairly well with the calculated results obtained through the solution of the Maxwell-Garnett equation, but the latter fails to predict the transition present in the composition versus optical constant curves of both materials. © 2002 American Vacuum Society.
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78.66.Nk Insulators
68.55.-a Thin film structure and morphology
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Amorphous silicon driver circuits for organic light-emitting diode displays

P. Servati, S. Prakash, A. Nathan, and Christoph Py

J. Vac. Sci. Technol. A 20, 1374 (2002); http://dx.doi.org/10.1116/1.1486006 (5 pages) | Cited 28 times

Online Publication Date: 27 June 2002

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This article presents design considerations pertinent to amorphous silicon (a-Si:H) pixel drive circuits for mobile display applications. We describe both pixel architectures and circuit topologies that are amenable for vertically stacked organic light-emitting diode (OLED) pixels in a-Si:H technology. Here, a dual-gate transistor structure is used to minimize the parasitic coupling between the OLED and the transistor layers. We consider both the two-transistor (2-T) voltage-programmed drive circuit and the five-transistor (5-T) current-programmed drive circuit. The latter provides compensation for shifts in device characteristics by virtue of metastable shifts in the threshold voltage of the thin-film transistor (TFT). Implementation of the 5-T drive circuit using dual-gate TFTs that enables high aperture ratio (∼100%), low leakage current, and surface emissive OLED pixels that are independent of scaling is also presented, along with simulation results of transfer characteristics. © 2002 American Vacuum Society.
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85.30.Tv Field effect devices
78.66.Jg Amorphous semiconductors; glasses
85.60.Pg Display systems

Anomalous growth of Ba on Ag(111)

O. M. N. D. Teodoro, J. Los, and A. M. C. Moutinho

J. Vac. Sci. Technol. A 20, 1379 (2002); http://dx.doi.org/10.1116/1.1486229 (5 pages) | Cited 2 times

Online Publication Date: 27 June 2002

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Electropositive elements are often adsorbed on metals to produce a well-known decrease in the surface work function. During deposition, the work function drops steeply and reaches a minimum at coverage lower than one monolayer. Then, it increases slightly and the work function converges to the value of the deposited element. In this work, we report anomalous behavior found during the deposition of barium on a Ag(111) surface. After a minimum of about 2.4 eV the work function did not increase up to 2.7 eV, the bulk barium work function, no matter what amount of barium was deposited. Auger electron spectroscopy corroborated these results in which we measured a permanent and constant intensity of the Ag MNN peak for high barium coverage. To explain this anomalous growth of barium on Ag(111) we propose an explanation based on the diffusion of silver atoms into the barium film. Further experiments showed that coadsorption of oxygen before a second deposition of barium blocked the diffusion thus allowing the work function to reach 2.7 eV. © 2002 American Vacuum Society.
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81.05.Bx Metals, semimetals, and alloys
81.15.Pq Electrodeposition, electroplating
73.30.+y Surface double layers, Schottky barriers, and work functions
79.20.Fv Electron impact: Auger emission
68.43.Mn Adsorption kinetics

Bakeable, all-metal demountable vacuum seal to a flat glass surface

N. Ng, R. E. Collins, and M. Lenzen

J. Vac. Sci. Technol. A 20, 1384 (2002); http://dx.doi.org/10.1116/1.1486228 (6 pages) | Cited 2 times

Online Publication Date: 27 June 2002

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A technique is described for making a demountable vacuum seal of reasonably good quality between an all-metal evacuation cup and a flat glass surface. The seal is bakeable to temperatures close to the softening point of glass. The stainless steel evacuation cup has two concentric and coplanar sealing surfaces. The regions defined by these surfaces are differentially pumped. Pressures typically below 1 Torr are achieved in the annular space between the two sealing surfaces using a conventional rotary pump. The center region inside the inner sealing surface is typically evacuated to below 10−4 Torr using conventional diffusion or turbomolecular pumps. © 2002 American Vacuum Society.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Microstructure and mechanical properties of nanocomposite amorphous carbon films

P. Zhang, B. K. Tay, C. Q. Sun, and S. P. Lau

J. Vac. Sci. Technol. A 20, 1390 (2002); http://dx.doi.org/10.1116/1.1486227 (5 pages) | Cited 22 times

Online Publication Date: 27 June 2002

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Nanocomposite amorphous carbon films such as a-C:Al, a-C:Ti, and a-C:Si have been prepared using a filtered cathodic vacuum arc technique. The films were characterized using x-ray photoelectron spectroscopy (XPS), atomic force microscopy, surface profilometry, a nanoindenter, and Raman spectrometry. It was found that metal contents in the films deviate from the target depending on the constituent element, which is attributed to the effect of dynamic balance deposition. XPS results revealed the presence of a carbide phase in a-C:Ti and a-C:Si but not in a-C:Al nanocomposite carbon films. Incorporating metal into amorphous carbon films significantly reduces the compressive stress but maintains the relative high hardness and Young’s modulus. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
79.60.Dp Adsorbed layers and thin films
68.37.Ps Atomic force microscopy (AFM)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Characterization of cubic boron nitride growth using UV-extended real-time spectroscopic ellipsometry: Effect of plasma additions and dynamic substrate bias steps

J. A. Zapien, R. W. Collins, and R. Messier

J. Vac. Sci. Technol. A 20, 1395 (2002); http://dx.doi.org/10.1116/1.1486226 (13 pages) | Cited 5 times

Online Publication Date: 27 June 2002

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Boron nitride (BN) films with high cubic content were deposited using pulsed dc sputtering of a B4C target and rf biasing of the substrate. The film deposition was characterized using ultraviolet-extended real-time spectroscopic ellipsometry (UV-RTSE). A three-layer optical model with constrained evolution of the layer thicknesses was used to characterize the growth of the BN films on c-Si substrates. This model was chosen for consistency with previous research and includes (i) an initial hexagonal BN (hBN) layer; (ii) a hexagonal+cubic BN (hBN+cBN) mixed-phase transition layer; and (iii) a topmost cBN layer. The evolution of the layer thicknesses was obtained as a function of the substrate bias (Vavg) used to deposit the BN films under static conditions. These results showed a minimum in the thicknesses of the hBN and mixed-phase layers, thus identifying an optimum Vavg for cBN nucleation and growth from the hBN phase under the deposition conditions used here. Complementary ex situ infrared transmission spectroscopy confirmed that UV-RTSE provides high sensitivity for resolving the crystallographic phase of BN due to differences in the hBN and cBN optical functions. The model with constrained evolution of thicknesses was also applied to determine the phase evolution of BN under dynamic conditions in which the substrate bias magnitude ∣Vavg∣ was decreased in a stepwise manner during deposition. As a result, the critical substrate bias voltage VCm needed to sustain pure cBN growth was determined. It was found that for ∣Vavg∣<∣VCm∣ a second hBN+cBN mixed-phase layer evolves and that upon further reduction in ∣Vavg∣ an onset for the formation of a pure hBN layer appears. The effects of plasma additions of hydrogen and oxygen on the BN phase evolution and the cBN optical properties were documented in dynamic ∣Vavg∣ step-down experiments. It was found that any additions of hydrogen or oxygen gas are detrimental when used under otherwise optimum cBN growth conditions, meaning that these additions promote the growth of hBN. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
78.66.Fd III-V semiconductors
81.15.Cd Deposition by sputtering

Evolution of tungsten film deposition induced by focused ion beam

H. Langfischer, B. Basnar, H. Hutter, and E. Bertagnolli

J. Vac. Sci. Technol. A 20, 1408 (2002); http://dx.doi.org/10.1116/1.1486230 (8 pages) | Cited 12 times

Online Publication Date: 27 June 2002

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Direct write metallization is an important approach for circuit modification and prototyping. We investigate the evolution of the chemical vapor deposition of tungsten induced by a 50 keV focused Ga+ ion beam. Time resolved imaging in combination with atomic force microscopy reveals that chemical vapor deposition of tungsten by focused ion beam proceeds via two clearly distinguishable regimes of layer growth. Deposition starts with the nucleation of nanoscale tungsten deposits scattered over the substrate surface. Despite local impacts of the ion beam within the irradiated area of the substrate the localization of the nucleation spots is not correlated to the scan path of the ion beam. The nanoscale tungsten particles preserve their position and typical shape during further deposition. Only after merging of the particles into a contiguous tungsten layer, does the second regime of growth characterized by deposition of tungsten on a tungsten surface set in. In this regime the deposition process is determined by the total ion dose and the average current density the sample was subjected to. Deposition yields up to 3.5 atoms per incident gallium ion are achieved. The layer quality is determined by Auger electron analysis, which shows fractions of Ga, C, Si and O in the W layer. Depth profiling by secondary ion mass spectroscopy showed the depth profiles of these constituents and confirmed the existence of a 50–100 nm thick transition zone between the tungsten layer and the substrate. Electrical resistivity of metal layers of 250 μ Ω cm and current densities up to 3.5×106 A/cm2 are measured by means of van der Pauw test structures. In order to give a concise description of the experimental findings the data were interpreted utilizing an analytic model that mainly incorporates the precursor gas coverage, precursor gas transformation cross section and ion induced sputtering. The critical ion current density, where ion sputtering exceeds the deposition, was identified by the model. Because the model shows excellent agreement with the measurement it should be suitable for a further survey of focused ion beam process development. © 2002 American Vacuum Society.
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68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Jj Ion and electron beam-assisted deposition; ion plating
85.40.Ls Metallization, contacts, interconnects; device isolation
68.37.Ps Atomic force microscopy (AFM)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.S- Impurities in crystals
73.61.At Metal and metallic alloys
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Surface and microstructural characterization of laser beam welds in an aluminum alloy

P. A. P. Nascente, C. Bolfarini, C. L. Benassi, N. G. Alcȃntara, and J. F. Santos

J. Vac. Sci. Technol. A 20, 1416 (2002); http://dx.doi.org/10.1116/1.1487868 (4 pages) | Cited 1 time

Online Publication Date: 27 June 2002

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The weldability of aluminum alloys is one of the main requirements to be considered for their application in the automotive and aerospace industry. In this work, the weld joints of an AA7020 alloy obtained by laser process were characterized by scanning electron microscopy, energy-dispersive x-ray spectrometry, wavelength-dispersive x-ray spectrometry, and x-ray photoelectron spectroscopy. The laser process can be described as a high-speed solidification process. The solidification rate can be estimated from the correlation among several solidification rates and the corresponding dendritic/cellular spacings, and the value calculated for this rate was 3.0×103 K/s. The inclusions present in the base metal were identified as (Cr,Fe)4Si4Al13, which were not observed in the fused zone. The fused zone microstructure showed two distinct phases: an aluminum solid solution and fine precipitates of MgZn2. The transition from the base metal to the fused zone presented a narrow heat-affected zone. A strong depletion of Zn was observed, and this does not influence the hot tearing susceptibility since hot cracks were not observed in the weld zone. © 2002 American Vacuum Society.
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81.20.Vj Joining; welding
68.35.B- Structure of clean surfaces (and surface reconstruction)
42.62.Cf Industrial applications
81.30.Fb Solidification
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Behavior of fluorocarbon species near temperature controlled and radio frequency biased metal plate in C4F8 plasma

Hyun-Ho Doh and Yasuhiro Horiike

J. Vac. Sci. Technol. A 20, 1420 (2002); http://dx.doi.org/10.1116/1.1487869 (6 pages) | Cited 4 times

Online Publication Date: 27 June 2002

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Variations of fluorocarbon species were investigated in the vicinity of metal stage that was installed in C4F8 inductively coupled plasma system with the parameters such as temperature of the stage, distance from the stage, gas residence time, and rf bias voltage applied to the stage. Quadrupole mass analyzer and appearance mass spectrometry have been used for the measurement of fluorocarbon ions, radicals. Densities of all radicals increased with the increase of stage temperature and the decrease of the gap distance between stage and detection point. On the other side, the concentrations of fluorocarbon ions decreased slightly when the stage temperature went down. It has been investigated that the density variation of the radicals dependent on the stage temperature could be controlled with gas residence time. It is considered that the balance between pumping loss rate and surface loss rate has a responsibility for the residence time effects on radical density variations. Finally, constant amounts of radicals were desorbed from the stage along with discharge time when we applied rf bias to the stage. All of the experimental results suggest that dielectric etching chamber should be designed on the basis of the understanding on plasma–wall interaction. © 2002 American Vacuum Society.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.25.-b Plasma properties
52.77.Bn Etching and cleaning
52.70.Gw Radio-frequency and microwave measurements

Monolithic multiple wavelength ridge waveguide laser array fabricated by Nd:YAG laser-induced quantum well intermixing

J. J. Dubowski, Y. Feng, P. J. Poole, M. Buchanan, S. Poirier, J. Genest, and V. Aimez

J. Vac. Sci. Technol. A 20, 1426 (2002); http://dx.doi.org/10.1116/1.1487876 (4 pages) | Cited 4 times

Online Publication Date: 27 June 2002

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Maskless selective area cw Nd:YAG laser annealing of GaInAsP/InP quantum well (QW) structures has been investigated as a possible route towards the fabrication of monolithically integrated photonic circuits. Laser irradiation of a 5 QW laser structure, originally designed for lasers emitting at 1.52 μm, yielded material having a continuously changing band gap ranging from 1.52 to 1.4 μm over the distance of about 3 mm. Bars with arrays of ridge waveguide lasers, having cavity lengths from 300 to 600 μm, were fabricated from the processed material. An individual bar, 2–3 mm long, comprised lasers operating typically between 1.4 and 1.52 μm. The lasers showed stable threshold current density and high quantum efficiency at all operating wavelengths. The results indicate that the applied approach has the potential to realize the cost-effective fabrication of advanced photonic devices and photonic integrated circuits. © 2002 American Vacuum Society.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.82.Cr Fabrication techniques; lithography, pattern transfer
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
42.60.By Design of specific laser systems

Calculated energy transfer in an accommodation pump

J. P. Hobson

J. Vac. Sci. Technol. A 20, 1430 (2002); http://dx.doi.org/10.1116/1.1487877 (4 pages)

Online Publication Date: 27 June 2002

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In an accommodation pump gas is transferred from one point to another at the same temperature without the application of any external mechanical or electrical forces to the gas—only temperature gradients are used. If there is no continuous flow a static and unchanging pressure difference develops between the two points, requiring no additional input of energy to the gas. Little attention has been paid to the energy transfer, i.e., the number of calories per mole of gas pumped, in this process. A simple model is presented in which this energy transfer is analytically calculated for a single-stage Pyrex accommodation pump, upper temperature room (295 K), lower temperature liquid nitrogen (77.4), gas helium, compression ratio 1.2, and pressure in the free molecular range. Under these conditions the physical adsorption of helium on pump surfaces is quantitatively negligible. The model calculates the energy difference between a true accommodation pump with atomically rough (leached) and smooth surfaces and a nonpump with exactly the same geometrical dimensions, but with all surfaces rough. The energy differences are assigned to accommodation pumping. It is found that an energy in the range of 300 calories per mole of gas pumped is required, independent of the overall size of the pump, but becoming smaller as the cold volume is reduced relative to the warm volume. The results are extended to multistage pumps, which are ponderous to calculate analytically, but which bear a simple relationship to a single-stage pump. © 2002 American Vacuum Society.
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47.45.Dt Free molecular flows
47.45.Gx Slip flows and accommodation
47.80.-v Instrumentation and measurement methods in fluid dynamics

Nanocomposite tribological coatings with “chameleon” surface adaptation

A. A. Voevodin, T. A. Fitz, J. J. Hu, and J. S. Zabinski

J. Vac. Sci. Technol. A 20, 1434 (2002); http://dx.doi.org/10.1116/1.1487875 (11 pages) | Cited 43 times

Online Publication Date: 27 June 2002

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Nanocomposite tribological coatings were designed to respond to changing environmental conditions by self-adjustment of their surface properties to maintain good tribological performance in any environment. These smart coatings have been dubbed “chameleon” because, analogous to a chameleon changing its skin color to avoid predators, the coating changes its “skin” chemistry and structure to avoid wear. The concept was originally developed using WC, diamondlike carbon, and WS2 material combination for adaptation to a humid/dry environment cycling. In order to address temperature variation, nanocomposite coatings made of yttria-stabilized zirconia (YSZ) in a gold matrix were developed with encapsulated nanosized reservoirs of MoS2 and diamondlike carbon (DLC). Coatings were produced using a combination of laser ablation and magnetron sputtering. They were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, x-ray energy dispersive spectroscopy, and micro-Raman spectroscopy. Results were correlated with mechanical and tribological characterization. Coating hardness was evaluated using nanoindentation, while coating adhesion and toughness were estimated using scratch and Vickers indentation tests. Friction and wear endurance measurements of YSZ/Au/MoS2/DLC coatings against steel and Si3N4 balls were performed at room temperature in controlled humidity air, dry nitrogen, and vacuum environments, as well as at 500 °C in air. Depending on the environment, coating friction surface changed its chemistry and structure between (i) graphitic carbon for sliding in humid air [coating friction coefficients (c.o.f. 0.10–0.15)], (ii) hexagonal MoS2 for sliding in dry N2 and vacuum (c.o.f. 0.02–0.05), and (iii) metallic Au for sliding in air at 500 °C (c.o.f. 0.10–0.20). The unique coating skin adaptation realized with YSZ/Au/MoS2/DLC and WC/DLC/WS composites proves a universal applicability of the chameleon design concept. © 2002 American Vacuum Society.
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81.40.Pq Friction, lubrication, and wear
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
68.55.-a Thin film structure and morphology
81.65.-b Surface treatments
79.60.Dp Adsorbed layers and thin films
68.37.Lp Transmission electron microscopy (TEM)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
78.30.Hv Other nonmetallic inorganics
78.66.Sq Composite materials

Unique structure/properties of chemical vapor deposited parylene E

Jay J. Senkevich, Christopher J. Mitchell, Aravind Vijayaraghavan, Edward V. Barnat, John F. McDonald, and Toh-Ming Lu

J. Vac. Sci. Technol. A 20, 1445 (2002); http://dx.doi.org/10.1116/1.1487870 (5 pages) | Cited 3 times

Online Publication Date: 27 June 2002

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Parylene E, a low κ polymer thin film, with the approximate composition 69% diethylated and 25% monoethylated poly(p-xylylene), has been chemical vapor deposited via a cyclophane precursor at room temperature. It has a dielectric constant of 2.34±0.03 and dielectric loss of <0.005 at 10 kHz from MIMCAP structures. It is particularly unique compared to the other common parylene polymers. Namely, it is nearly optically isotropic and it is soluble in common laboratory solvents such as methylene chloride, chloroform, and toluene. It is shown to have an optical birefringence of −0.0112 at 634.1 nm and a correspondingly low degree of crystallization after a 150 °C postdeposition anneal. The low degree of crystallization results in a smooth film (10 Å rms surface roughness for a 2060 Å thin film) with no optical loss (in reflection mode), i.e., an extinction coefficient of zero. These properties for parylene E make it appropriate for use as an optical waveguide and for archival conservation or other applications where low optical loss or film removal might be necessary. © 2002 American Vacuum Society.
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77.84.Jd Polymers; organic compounds
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
78.66.Qn Polymers; organic compounds
42.70.Jk Polymers and organics
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
64.75.-g Phase equilibria
78.20.Fm Birefringence
61.41.+e Polymers, elastomers, and plastics
68.35.B- Structure of clean surfaces (and surface reconstruction)

Study on modification of hydrogen trap site in nickel and stainless steel using atom probe

Toshihiko Yoshimura and Yuichi Ishikawa

J. Vac. Sci. Technol. A 20, 1450 (2002); http://dx.doi.org/10.1116/1.1487874 (8 pages) | Cited 1 time

Online Publication Date: 27 June 2002

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Nickel and aged stainless steel that was composed of nanometer-scale Cr-rich and Fe-rich regions were chosen as model systems for the modification of hydrogen-trap sites. Nickel and stainless steel were annealed and oxidized to modify the types and numbers of hydrogen-trap sites. Deuterium was used in this experiment to enhance the detectability of hydrogen isotope detected in the atom probe analysis. Strongly bound deuterium trap sites are observed and have a higher density than the solubility in lattice. The amount of deuterium trapped in nickel decreases after annealing. This is a result of the modification of trap sites by annealing. Deuterium trapped in the oxide layer and in the oxide–nickel interface of nickel was observed at a sufficient resolution to determine the extent of trapping on an atomic scale, and thus to gather quantitative data on the modification of trap sites by oxidation. The deuterium atoms are trapped into the Cr-rich region on the ferritic phase of duplex stainless steel. The deuterium atoms trapped are associated with nickel atoms and oxygen atoms. © 2002 American Vacuum Society.
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61.72.S- Impurities in crystals
81.65.Mq Oxidation
61.72.Cc Kinetics of defect formation and annealing
68.37.Vj Field emission and field-ion microscopy
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
81.40.Gh Other heat and thermomechanical treatments

Low frictional coating by cosputtering in combination with excimer laser irradiation for aerospace applications

Masahiro Goto, Akira Kasahara, Masahiro Tosa, Jonathan Hobley, Maki Kishimoto, Kazuhiro Yoshihara, and Hiroshi Fukumura

J. Vac. Sci. Technol. A 20, 1458 (2002); http://dx.doi.org/10.1116/1.1487873 (4 pages) | Cited 5 times

Online Publication Date: 27 June 2002

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Low frictional coatings made of copper, boron nitride, and oxygen on a stainless steel substrate were synthesized by magnetron cosputter deposition combined with excimer laser irradiation. The frictional force of the coating films was observed by a system developed for measuring vacuum friction. The coating properties were also observed by a conventional contact angle measuring system, a scanning Auger electron spectrometer, and a Vickers hardness measuring system. The surface layer of the coating films was oxidized by the excimer laser irradiation. Surface energy and film hardness were also modified by the laser irradiation. Frictional coefficients as low as 0.075 were achieved after irradiating the films under ultrahigh vacuum conditions. Since these coating films have already been oxidized and irradiated with high energy UV light they will be applicable for aerospace coatings. © 2002 American Vacuum Society.
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81.15.Cd Deposition by sputtering
81.15.Fg Pulsed laser ablation deposition
81.65.Mq Oxidation
62.20.Qp Friction, tribology, and hardness
68.35.Af Atomic scale friction

Phase behavior in the CdTe–CdS pseudobinary system

Brian E. McCandless, Gregory M. Hanket, D. Garth Jensen, and Robert W. Birkmire

J. Vac. Sci. Technol. A 20, 1462 (2002); http://dx.doi.org/10.1116/1.1487872 (6 pages) | Cited 7 times

Online Publication Date: 27 June 2002

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Polycrystalline thin films deposited by coevaporation of CdTe and CdS form metastable single-phase CdTe–CdS alloys. Subsequent heating in a kinetic-enhancing ambient segregates CdTe1−xSx and CdS1−yTey phases from the original alloy phase. The equilibrium miscibility gap between the resulting CdTe1−xSx and CdS1−yTey alloy phases is determined for CdTe1−xSx films with initial x ∼ 0.4 treated from 360 to 700 °C. At 625 °C, the equilibrium compositions correspond to published results for mixed crystals. Below 625 °C the miscibility gap widens asymmetrically due to different mixing free energies for S in CdTe and Te in CdS. The solubility thermodynamics are modeled with an excess mixing free energy to account for nonideal mixing behavior. © 2002 American Vacuum Society.
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68.55.Nq Composition and phase identification
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
81.40.Gh Other heat and thermomechanical treatments
81.05.Dz II-VI semiconductors
65.40.G- Other thermodynamical quantities

Thickness-dependent microstructural and electrochromic properties of sputter-deposited Ni oxide films

Kwang-Soon Ahn, Yoon-Chae Nah, and Yung-Eun Sung

J. Vac. Sci. Technol. A 20, 1468 (2002); http://dx.doi.org/10.1116/1.1487871 (7 pages) | Cited 10 times

Online Publication Date: 27 June 2002

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Thickness-dependent microstructural and electrochromic properties of sputter-deposited Ni oxide films were investigated as a function of growth time using x-ray diffraction, in situ transmittance measurements, and x-ray photoelectron spectroscopy. By increasing the thickness of the Ni oxide, the transmittance or optical differences during coloring/bleaching process were increased. However, thick Ni oxides showed a lower maximum bleached transmittance and coloration efficiency and a larger response time. Crystallinity developed with growth time, mainly due to the plasma heating effect. The evolution of crystallinity with the growth time resulted in the electrochromic inactive Ni oxide components even after several tens of potential cyclings, leading to a decreased maximum bleached transmittance and lower coloration efficiency. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
78.20.Jq Electro-optical effects
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.66.-w Optical properties of specific thin films
82.45.Mp Thin layers, films, monolayers, membranes
79.60.Dp Adsorbed layers and thin films

Surface phase transitions of Pt(110) studied by desorption dynamics of product CO2 in steady-state CO oxidation

I. Rzeznicka, L. Morales de la Garza, and T. Matsushima

J. Vac. Sci. Technol. A 20, 1475 (2002); http://dx.doi.org/10.1116/1.1488945 (6 pages) | Cited 3 times

Online Publication Date: 27 June 2002

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The transformation of (1×2) into (1×1) on a Pt(110) surface in the course of CO oxidation was studied through the analysis of both angular and velocity distributions of desorbing product CO2 and low-energy electron diffraction (LEED) intensity. The intensity of half-order LEED spots decreased quickly, showing the beginning of the transformation of (1×2)→(1×1) just below the kinetic transition, where the rate-determining step switched from CO adsorption to O2 dissociation. On the other hand, the angular distribution of desorbing CO2 sharply changed at a CO pressure far above the kinetic transition, where (1×2) domains disappeared. Below this approximate CO pressure, CO2 was mostly formed on (1×2) domains regardless of its reduced area. © 2002 American Vacuum Society.
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68.35.Rh Phase transitions and critical phenomena
68.43.Mn Adsorption kinetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.65.Mq Oxidation

Physical properties of nitrogen-doped diamond-like amorphous carbon films deposited by supermagnetron plasma chemical vapor deposition

Haruhisa Kinoshita and Naoki Otaka

J. Vac. Sci. Technol. A 20, 1481 (2002); http://dx.doi.org/10.1116/1.1488946 (5 pages) | Cited 5 times

Online Publication Date: 27 June 2002

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Diamond-like amorphous carbon films doped with nitrogen (DAC:N) were deposited on Si and glass wafers intermittently using i-C4H10/N2 repetitive supermagnetron plasma chemical vapor deposition. Deposition duration, which is equal to a plasma heating time of wafer, was selected to be 40 or 60 s, and several layers were deposited repetitively to form one thick film. DAC:N films were deposited at a lower-electrode temperature of 100 °C as a function of upper- and lower-electrode rf powers (200 W/200 W–1 kW/1 kW) and N2 concentration (0%–80%). With an increase in N2 concentration and rf power, the resistivity and the optical band gap decreased monotonously. With increase of the deposition duration from 40 to 60 s, resistivity decreased to 0.03Ω cm and optical band gap decreased to 0.02 eV (substantially equal to 0 eV within the range of experimental error), at an N2 concentration of 80% and rf power of 1 kW(/1 kW). © 2002 American Vacuum Society.
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81.05.U- Carbon/carbon-based materials
61.43.Dq Amorphous semiconductors, metals, and alloys
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
52.77.Dq Plasma-based ion implantation and deposition
73.61.Jc Amorphous semiconductors; glasses
78.66.Jg Amorphous semiconductors; glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Surface morphology of evaporated CuInS2 thin films grown by single source thermal evaporation technique

Youji Akaki, Hironori Komaki, Kenji Yoshino, and Tetsuo Ikari

J. Vac. Sci. Technol. A 20, 1486 (2002); http://dx.doi.org/10.1116/1.1488944 (2 pages) | Cited 4 times

Online Publication Date: 27 June 2002

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Single source thermal evaporation technique was carried out for CuInS2 thin films on the glass substrates. The films were annealed from 100 °C to 500 °C in air. The crystal structures of the films were examined by x-ray diffraction and surface morphology investigated by optical microscope. The CuInS2 thin films were grown by annealing at 200 °C. The sample indicated high resistivity and n-types conductivity examined by a four-point probe method and thermoprobe analysis, respectively. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Le Other inorganic semiconductors
72.80.Ga Transition-metal compounds
81.40.Gh Other heat and thermomechanical treatments

Density and temperature in an inductively amplified magnetron discharge for titanium deposition

A. Ricard, C. Nouvellon, S. Konstantinidis, J. P. Dauchot, M. Wautelet, and M. Hecq

J. Vac. Sci. Technol. A 20, 1488 (2002); http://dx.doi.org/10.1116/1.1488948 (4 pages) | Cited 29 times

Online Publication Date: 27 June 2002

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In order to determine the titanium neutral density, a direct current (dc) plasma discharge, amplified by a radio-frequency (rf) coil, was studied by absorption spectrometry. The argon pressure varied from 5 to 40 mTorr. The dc and rf powers varied between 100 and 1500 W and 0 and 500 W, respectively. The plasma gas temperature necessary for the density calculation was evaluated by analyzing the N2 rotational spectrum in an Ar–N2 gas mixture. When increasing the rf power a decrease of titanium neutral density was found. This decrease is related to the increased titanium ion density. When using the rf coil, the titanium degree of ionization can be up to 90%. © 2002 American Vacuum Society.
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52.25.-b Plasma properties
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating

GaAs surface cleaning by low energy hydrogen ion beam treatment

N. Razek, K. Otte, T. Chassé, D. Hirsch, A. Schindler, F. Frost, and B. Rauschenbach

J. Vac. Sci. Technol. A 20, 1492 (2002); http://dx.doi.org/10.1116/1.1488949 (6 pages) | Cited 10 times

Online Publication Date: 27 June 2002

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A technology of semiconductor surface cleaning has been applied to GaAs surfaces for the preparation of contamination free surfaces. This technique combines a low energy hydrogen ion beam (ion energy <500 eV) with an increased substrate temperature (150 °C). The long term change of the GaAs (001) surface composition under the influence of this process was investigated with in situ x-ray photoelectron spectroscopy and atomic force microscopy. A removal of surface oxides and carbon as well as of surface contaminations due to the hydrogen ion beam treatment could be observed. At an elevated substrate temperature of 150 °C, the hydrogen ion beam produces a contamination-free surface without changes in surface composition (stoichiometry) or surface roughness, whereas room temperature hydrogen exposure results in an As-depleted surface composition. This technique could be used for wafer direct bonding of III–V semiconductors and other processes which require highly efficient quality cleaning procedures. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.Dv Composition, segregation; defects and impurities
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.37.Ps Atomic force microscopy (AFM)

Effects of deposition temperature and seed layer on the optical properties of lead zirconate titanate films

Hee-Soo Kang and Won-Jong Lee

J. Vac. Sci. Technol. A 20, 1498 (2002); http://dx.doi.org/10.1116/1.1488947 (7 pages) | Cited 11 times

Online Publication Date: 27 June 2002

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Lead zirconate titanate (PZT) films were deposited on indium tin oxide coated Corning 7059 glass by rf magnetron sputtering at the temperatures ranging from room temperature to 500 °C. The crack-free PZT films with pure perovskite phase could be successfully fabricated through postannealing at 650 °C for 10 min. The films deposited at 400 °C and subsequently postannealed at 650 °C showed the best optical properties with a linear electro-optic coefficient of 80 pm/V and a propagation loss of 2 dB/cm. It was found from our study on the change of crystalline orientation with film thickness that the 50 nm thick PZT thin film annealed at 650 °C exhibited (100) preferred orientation. Using this thin film as a seed layer, we could fabricate PZT films with (100) preferred orientation that showed higher remnant polarization (2Pr=46 μC/cm2) and dielectric constant (ϵ=1400) compared with randomly oriented films. This highly oriented PZT film also showed an excellent linear electro-optic coefficient of 109 pm/V that is comparable with the value of the PZT film epitaxially grown on the single crystal substrate. © 2002 American Vacuum Society.
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81.15.Cd Deposition by sputtering
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.66.Nk Insulators
77.80.-e Ferroelectricity and antiferroelectricity
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
78.20.Jq Electro-optical effects
68.55.-a Thin film structure and morphology
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
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