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Nov 1990

Volume 8, Issue 6, pp. 3907-4119


The role of sputter redeposition in the growth of cones and filaments on carbon surfaces during ion bombardment

W. A. Solberg and I. L. Spain

J. Vac. Sci. Technol. A 8, 3907 (1990); http://dx.doi.org/10.1116/1.576418 (3 pages)

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Cones topped by filaments with submicron diameters grow on carbon surfaces when they are bombarded with energetic (e.g., 1 keV) argon ions. It is shown that sputter redeposition is an important process by which cone growth occurs. The possible role of hydrogen in poisoning growth sites and increasing the density of cones at higher temperature is discussed. Several experiments are proposed to clarify growth mechanisms.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)

Magnetron sputtered boron films and Ti/B multilayer structures

D. M. Makowiecki, A. F. Jankowski, M. A. McKernan, and R. J. Foreman

J. Vac. Sci. Technol. A 8, 3910 (1990); http://dx.doi.org/10.1116/1.576419 (4 pages) | Cited 3 times

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Boron and Ti/B films have been magnetron sputter deposited and characterized using x‐ray diffraction, Auger‐depth profiling, and electron microscopy. The amorphous boron films contain no morphological growth features, unlike those characteristically found in thin films prepared by various plasma vapor deposition processes. The use of a high‐density boron sputter target prepared by hot isostatic pressing was a major factor in controlling the deposition process. Consequently, the radio frequency sputter deposited boron proves feasible for ultrathin band pass filters as well as the low Z element in high Z/low Z mirrors which enhance reflectivity from grazing to normal incidence.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
61.43.Fs Glasses
61.43.-j Disordered solids
61.44.Br Quasicrystals

Sloped niobium etching using CF4 and O2

Jay N. Sasserath and John Vivalda

J. Vac. Sci. Technol. A 8, 3914 (1990); http://dx.doi.org/10.1116/1.576420 (6 pages)

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A sloped etching process for Nb is developed for pilot line operations. Reactive ion etching and plasma processes are compared for a CF4/O2 parallel plate etch system. The higher pressure etches were found to have better characteristics for the numerous combinations of independent variables examined. Process settings tested include rf power, chamber pressure, and etchant flow rates. Higher Nb etch rates, photoresist:niobium etch rate selectivity of 1:1, and adequate selectivity over SiO2 were obtained with the plasma etches. For both types of processes, control of plasma loading affects were determined to be crucial to accomplish successful patterning. Finally, mathematical models of the etch process were derived from the data and used to determine basic etch mechanisms occurring within the reactor.
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81.05.Bx Metals, semimetals, and alloys
85.40.Hp Lithography, masks and pattern transfer

Laser‐induced fluorescence characterization of ions in a magnetron plasma

M. J. Goeckner, J. Goree, and T. E. Sheridan

J. Vac. Sci. Technol. A 8, 3920 (1990); http://dx.doi.org/10.1116/1.576421 (5 pages) | Cited 21 times

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We report for the first time laser‐induced fluorescence measurements of a sputtering magnetron plasma. From these measurements we determined the density, average velocity, and temperature of the ions. The ion density profile is peaked at the same location as the electron density profile, which was measured with a Langmuir probe. The average ion velocity parallel to the cathode surface is less than our detection limit of 93 m/s. The ions at the edge of the discharge are room temperature, while in the center of the discharge they reach a temperature of 0.64 eV. These temperatures are attributed to acceleration of the ions by the electric field in the plasma, together with collisional scattering.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Process effects on radio frequency diode reactively sputtered ZrO2 films

M. M. Yang, T. M. Reith, and C. J. Lin

J. Vac. Sci. Technol. A 8, 3925 (1990); http://dx.doi.org/10.1116/1.576422 (4 pages) | Cited 4 times

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The ZrO2 thin film is deposited by means of a reactive radio frequency diode sputtering from an elemental zirconium target in an argon–oxygen mixture gas. The influence of the deposition process parameters on the microinstructure, composition, film stress, and refractive index is investigated. It is noted that the process parameters, in particular substrate bias, have a profound effect on the structure and properties. The possible mechanism, in terms of bombardment of energetic particles and adatom mobility on the film surface, is discussed.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic

Composition and structure of boron nitride films deposited by chemical vapor deposition from borazine

J. Kouvetakis, V. V. Patel, C. W. Miller, and D. B. Beach

J. Vac. Sci. Technol. A 8, 3929 (1990); http://dx.doi.org/10.1116/1.576423 (5 pages) | Cited 6 times

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The composition and structure of boron nitride films prepared by thermal and plasma enhanced chemical vapor deposition (CVD) using borazine as a precursor have been studied. Thermal CVD at temperatures between 475 and 550 °C using either a hot‐wall or cold‐wall reactor results in amorphous boron‐rich films of approximate composition BN0.67. Plasma enhanced CVD consistently gives films of 1:1 boron to nitrogen stoichiometry, but the hydrogen content of films deposited below 300 °C is so high that the films react with atmospheric moisture. Optimum conditions for the growth of stoichiometric BN with relatively low hydrogen content were found to be low plasma power, hydrogen–borazine gas mixtures, and a substrate temperature of 550 °C. Films deposited under these conditions are mixtures of poorly crystalline hexagonal and cubic boron nitride.
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68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

The growth of thin films with high thickness uniformity using ultrahigh vacuum molecular beam deposition

C. H. Hale, I. T. Muirhead, S. P. Fisher, J. S. Orr, J. G. H. Mathew, K. A. Prior, A. C. Walker, and S. D. Smith

J. Vac. Sci. Technol. A 8, 3934 (1990); http://dx.doi.org/10.1116/1.576424 (4 pages) | Cited 2 times

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Micrometer thick layers of ZnSe and other dielectric materials have been grown with high thickness uniformity using the new ultrahigh vacuum (UHV) molecular beam deposition (MBD) technique. Optical techniques have been employed to demonstrate that variations in thickness down to as little as ±0.15% over 90 mm diam can be achieved.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Copper oxide thin‐film growth using an oxygen plasma source

P. Luzeau, X. Z. Xu, M. Laguës, N. Hess, J. P. Contour, M. Nanot, F. Queyroux, M. Touzeau, and D. Pagnon

J. Vac. Sci. Technol. A 8, 3938 (1990); http://dx.doi.org/10.1116/1.576425 (3 pages) | Cited 11 times

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We present measurements of the oxidation level (Cu+ and Cu2+ concentration) of copper thin films deposited using a new type of oxygen plasma source. This oxygen plasma source is operated under ultrahigh vacuum, and allows one to oxidize copper up to nearly pure Cu2+ oxide at rather low temperature (<500 °C) and low molecular oxygen background pressure (2×10−6 Torr). High growth rate and high substrate temperature promote the formation of Cu+ oxide, whereas Cu2+ oxide is mainly obtained at low growth rate (0.5 Å s−1) and low substrate temperature (450 °C). The active species for oxidation is mostly atomic oxygen produced in the plasma. When the plasma is off, while the oxygen flux remains unchanged, no copper oxide is detected in the films.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Bx Metals, semimetals, and alloys

Tin foil reconstruction in a hydrogen plasma

C. H. Chou and Jonathan Phillips

J. Vac. Sci. Technol. A 8, 3941 (1990); http://dx.doi.org/10.1116/1.576426 (7 pages)

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As part of a continuing effort to characterize the influence of plasma environments on metals, tin foil reconstruction in argon, oxygen, and hydrogen plasma afterglows, created with a low power (<250 W) microwave system, was studied. It was found that neither oxygen nor argon plasmas had any apparent impact on the foil morphology. Hydrogen plasma treatments led to a dramatic reconstruction of the foils. Whereas originally the foil samples consisted of large, oriented crystals, following treatment in hydrogen plasmas the foil surfaces became a network of large pores and strings of small randomly oriented crystallites. No weight loss (etching) was observed. Detailed study and modeling work suggested that the reconstruction was the result of the formation of metastable tin hydride and subsequent short range metal transport. In contrast to the etching of other metals, ions, and electrons were found to play no role in the process.
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81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
81.05.Bx Metals, semimetals, and alloys
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Thermally stimulated exoelectron emission from glass deposited on metal by argon plasma treatment

Y. Momose and H. Takahashi

J. Vac. Sci. Technol. A 8, 3948 (1990); http://dx.doi.org/10.1116/1.576427 (6 pages) | Cited 3 times

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Argon plasma treatment of gold metal in a glass reactor deposited silicon oxide originating from the reactor on the metal surface. The deposited silicon oxide was nonstoichiometric and had a strong exoelectron emission activity. The chemical and structural nature of the emitting centers has been investigated. The thermally stimulated exoelectron emission (TSEE) glow curves for the surfaces exhibited one strong emission peak at ∼170 °C (in a few cases, three peaks at ∼120, 190, and 240 °C ) with increasing temperature. The intensity of the TSEE peak appearing at 170–190 °C varied in parallel to the atomic ratio of Si2p/O1s obtained by x‐ray photoelectron spectroscopy as a function of operational parameters in the plasma treatment. The TSEE peak intensity increased with an increase in the ratio of Si2p/O1s. The emitting centers for the TSEE peak can be related to electron trapping sites located in the neighborhood of the oxygen‐deficient silicon atoms deposited on the metal surface.
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77.22.Ej Polarization and depolarization
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Determination of electrode/substrate surface temperatures through the solid–liquid transition of metals/eutectics in capacitively coupled radio frequency‐plasma chemical vapor deposition reactors

M. Shinohara, H. Tashiro, K. Saio, K. Arai, and K. Takayama

J. Vac. Sci. Technol. A 8, 3954 (1990); http://dx.doi.org/10.1116/1.576428 (7 pages) | Cited 1 time

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In a capacitively coupled radio frequency‐plasma chemical vapor deposition reactor, we took pure metals, In, Sn, Bi, and Pb with the melting points ranging from 157 to 327 °C, and the eutectic Al (45 wt. %)/Ge alloy with the eutectic point of 423 °C as the fixed point materials to determine surface temperatures of the electrode and a piece of stainless steel (SLS) plate placed on it. The surface temperatures thus obtained were compared with temperatures detected with a thermocouple mounted within the electrode. An analysis of the obtained results based on a simplified heat transfer model revealed the thermal contact resistance at the specimen‐SLS plate interface to be as small as about one sixth that at an interface between two pieces of SLS plate. Criteria for the choice of eutectics as the thermometric fixed‐point materials are discussed and some possible candidates usable for this purpose are listed.
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07.20.Dt Thermometers
64.70.D- Solid-liquid transitions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Crystallographic and optical study of ZrO2 partially and totally stabilized with Y2O3

M. Mesbah, A. Boyer, E. Groubert, and L. Martin

J. Vac. Sci. Technol. A 8, 3961 (1990); http://dx.doi.org/10.1116/1.576429 (6 pages)

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We have studied the effects of the O2 concentration in the argon sputtering gas and the substrate temperature on the structural and optical properties of the totally stabilized zircone (TSZ) and partially stabilized zircone (PSZ) materials comparatively. In the TSZ material, the presence of molecules of the Y2O3 dopant reduces the effect of different deposition conditions on the film structure in regard to the PSZ material.
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78.66.-w Optical properties of specific thin films
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering

Ab initio simulation of the interaction between ionic crystal surfaces and the atomic force microscope tip

A. Shluger, C. Pisani, C. Roetti, and R. Orlando

J. Vac. Sci. Technol. A 8, 3967 (1990); http://dx.doi.org/10.1116/1.576430 (6 pages) | Cited 4 times

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The ab initio Hartree–Fock program crystal is used to simulate the interaction of three different kinds of tips of the atomic force microscope (AFM) with the MgO(100) surface, by employing the periodic slab model. The neutral silicon atom and the SiO molecule (Si or O oriented toward the surface) are used as tip models. The relevant AFM topographical resolution and its quality are analyzed. It is shown that, depending on the chemical and electronic structure of the tip, the interpretation of the images obtained could be even opposite. The best topographic image is expected for the weak constant force (≊2×10−8 N) repulsive regime between the tip and the ionic surface. Their mutual perturbation is studied in detail.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Observation of (5×1) surface reconstruction and surface smoothing of molecular‐beam epitaxial ZnS:Ga by post‐annealing

Shin‐ichi Ohta, Satoshi Kobayashi, Futao Kaneko, and Ko‐ichi Kashiro

J. Vac. Sci. Technol. A 8, 3973 (1990); http://dx.doi.org/10.1116/1.576431 (7 pages) | Cited 1 time

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The (2×1) and (5×1) surface reconstructions accompanied with the surface smoothing have been observed at ZnS:Ga layers grown on (100) GaAs by molecular‐beam epitaxy (MBE) and followed by postannealing at 600 °C for 20 min. The origin of these reconstructions are discussed and it is suggested that the reconstruction of (5×1) is due to the misfit strain relaxation in the ZnS:Ga epilayer or at the ZnS:Ga/GaAs interface. The simple lattice model of (2×1) and (5×1) surfaces are proposed on the basis of a dimer model. It is confirmed that the surface lattice models proposed give the diffraction patterns of (2×1) and (5×1) by a laser simulation.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Surface hydrogen–palladium studies using a new photopyroelectric detector

Andreas Mandelis and Constantinos Christofides

J. Vac. Sci. Technol. A 8, 3980 (1990); http://dx.doi.org/10.1116/1.576432 (4 pages) | Cited 3 times

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A new hydrogen gas trace detection principle based on a photopyroelectric solid‐state sensor has been developed. The sensor was made of thin commercially available polyvinylidene fluoride (PVDF) pyroelectric film, sputter coated with palladium (Pd). An infrared laser beam (800 nm) served to produce ac voltages due to the photopyroelectric effect. Exposure to hydrogen gas was shown to produce a differential signal between the Pd and reference electrodes. Accumulated experimental evidence has led us to tentatively attribute the detection principle to the adsorption, dissociation, and absorption of hydrogen molecules on the Pd surface, which caused a shift on the PVDF pyroelectric coefficient, due to electrostatic interactions of H+ ions with the PVDF polar molecular system at the Pd–PVDF interface. A quantitative interpretation of the hydrogen partial pressure dependence of the differential signal has been achieved using simple gas‐solid interaction theory and the combination of the Langmuir isotherm with photopyroelectric theory. The new detector could become an excellent tool for surface science studies under ultrahigh vacuum, especially at low temperatures where other sensors do not exhibit good performance.
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82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
77.70.+a Pyroelectric and electrocaloric effects
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Hydrogen chemisorption and reaction on GaAs(100)

J. R. Creighton

J. Vac. Sci. Technol. A 8, 3984 (1990); http://dx.doi.org/10.1116/1.576433 (4 pages) | Cited 12 times

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We have studied the chemisorption of atomic hydrogen and deuterium on gallium‐rich (4×6) and arsenic‐rich c(2×8) GaAs(100) reconstructed surfaces using temperature programmed desorption (TPD). Molecular hydrogen (specifically D2) desorption from the gallium‐rich (4×6) surface exhibits a peak at 480–510 K, depending on the initial coverage. By comparing results from the different reconstructions we conclude that the desorption of molecular hydrogen primarily arises from surface GaHx species. The arsenic‐rich c(2×8) surface yields a small amount of molecular hydrogen desorption around 660 K, apparently arising from surface AsHx species. In addition to molecular hydrogen, chemisorbed arsine is detected desorbing from both reconstructions around 330–340 K. This result indicates that atomic hydrogen can etch the GaAs surface. For the maximum exposure studied, ∼15% of the surface arsenic on the arsenic‐rich c(2×8) surface is converted to arsine.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.65.-b Surface treatments

Surface analysis of copper, brass, and steel foils exposed to fluorine containing atmospheres

A. L. Cabrera, E. J. Karwacki, and J. F. Kirner

J. Vac. Sci. Technol. A 8, 3988 (1990); http://dx.doi.org/10.1116/1.576434 (9 pages)

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The composition and thickness of fluoride films that form upon exposure of various metals to F2/N2 at room temperature were studied using x‐ray photoelectron and Auger electron spectroscopy (AES). Depth profiles were obtained using AES with argon ion sputtering. The metals studied included low carbon steel, 302 stainless steel, copper, and brass (70% Cu/30% Zn). Samples treated in 0.12% F2/N2 display small amounts of surface fluorine, primarily in the form of fluorinated hydrocarbons rather than metal fluorides. In contrast, exposure to 25% F2 produces thicker films, consisting mainly of metal fluorides with some metal oxides. Fluorine does not seem to penetrate beyond the native oxide initially present on the metal foil surface. Iron fluorides form on low carbon steel, and copper fluorides form on copper. Surprisingly, iron fluorides preferentially form on stainless steel, and zinc fluorides preferentially form on brass. These results provide new insight about the passivation of metals by F2 and raise new questions.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Optical second‐harmonic generation study of barium deposition on Si(001)

R. W. J. Hollering, D. Dijkkamp, H. W. L. Lindelauf, P. A. M. van der Heide, and M. P. C. M. Krijn

J. Vac. Sci. Technol. A 8, 3997 (1990); http://dx.doi.org/10.1116/1.576435 (4 pages) | Cited 4 times

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Experimental results are presented on the deposition of barium on clean Si(001) studied by optical second‐harmonic generation and work function measurements. Barium deposition up to one monolayer coverage enhances the signals by nearly a factor of 10. Continued deposition of Ba leaves the signal arising from the in‐plane polarization component unaffected, indicating that this signal arises from the Si–Ba interface or the Ba–vacuum interface. In contrast, the second‐harmonic signals related to the normal polarization components are increased by another order of magnitude around ∼4 ML Ba coverage.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
73.30.+y Surface double layers, Schottky barriers, and work functions
78.66.Bz Metals and metallic alloys

Divergence measurements for characterization of the micropatterning quality of broad ion beams

Ch. Huth, H.‐C. Scheer, B. Schneemann, and H.‐P. Stoll

J. Vac. Sci. Technol. A 8, 4001 (1990); http://dx.doi.org/10.1116/1.576436 (10 pages) | Cited 9 times

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For characterization of the micropatterning qualities of broad ion beam systems we introduce the concept of internal divergence in terms of the ion incidence angle distribution at a point of the processing plane. Methods for determination of this quality are discussed, and measurements are carried out for argon and oxygen for two different ion beam systems. Internal divergence is measured with a two‐stage Faraday cup assembly. Results for the divergence angle range from 3° to 9° for Ar as an operating gas, and the values for O2 are 10%–20% lower and show the same dependence on operating conditions of the source. Internal divergence within the beam center region is in good agreement with measured divergence values from literature, but deviates at the beam periphery. Divergence angles there are different primarily due to the discharge chamber plasma inhomogeneity. At high angular resolution of the two‐stage cup the beamlet structure of a broad beam can be revealed in both ion beam density and ion incidence angle. Consequences for the processing parameters of ion beam systems in micropatterning are deduced. Local measurement of the internal divergence within the processing plane turns out to be an adequate characterization of an ion beam system for large area etching applications.
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Ion energy measurements at the surface of an ion cyclotron range of frequencies antenna Faraday shield

J. B. O. Caughman, D. N. Ruzic, D. J. Hoffman, R. A. Langley, and M. B. Lewis

J. Vac. Sci. Technol. A 8, 4011 (1990); http://dx.doi.org/10.1116/1.576437 (6 pages)

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The effects of rf fields on the energy of ions hitting the surface of an ion cyclotron range of frequencies (ICFR) antenna exposed to a plasma must be investigated to provide an understanding of the impurity generation from the antenna. A resonant loop antenna with a two‐tier Faraday shield, installed on the Radio Frequency Test Facility at Oak Ridge National Laboratory, was used to study these effects. Samples of silicon were placed below the antenna and on the Faraday shield surface, facing the plasma, to measure incident ion energy. The samples were exposed to electron cyclotron heated plasmas without rf power and with 22 kW of rf power at antenna currents of up to 400 A. The fluence of ∼5×1017 D/cm2 from deuterium plasmas was near the saturation level of the samples. The energy of the incident ions was estimated by measuring the amount of deuterium trapped in the samples with D(3He,p)4 He nuclear reaction analysis. The results obtained from the trapped deuterium measurements are compared with ion energies measured directly with a gridded energy analyzer located near the antenna. They show that the rf‐enhanced ion energy distribution measured in the plasma is proportional to the impact energies on the surface of the Faraday shield and increases with antenna current.
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52.50.Gj Plasma heating by particle beams
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.40.Hf Plasma-material interactions; boundary layer effects

The effect of Sr and Bi on the Si(100) surface oxidation: Auger electron spectroscopy, low energy electron diffraction, and x‐ray photoelectron spectroscopy study

W. C. Fan, A. Mesarwi, and A. Ignatiev

J. Vac. Sci. Technol. A 8, 4017 (1990); http://dx.doi.org/10.1116/1.576438 (4 pages) | Cited 3 times

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The effect of Sr and Bi on the oxidation of the Si (100) surface has been studied by Auger electron spectroscopy, low electron diffraction, and x‐ray photoelectron spectroscopy. A dramatic enhancement, by a factor of 10, of the Si oxidation has been observed for Si(100) with a Sr overlayer. The SR‐enhanced Si oxidation has been studied as a function of O2 exposure and Sr coverage. In contrast to the oxidation promotion of Sr on Si, it has been also observed that a Bi overlayer on Si(100) reduced Si oxidation significantly. Sr adsorption on the Si(100) with a Bi overlayer enhances Si oxidation only at Sr coverage θSr >0.3 ML.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.65.-b Surface treatments
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Auger electron spectroscopy depth profile study in fracture surfaces of sinterized YBa2Cu3O7−x

J. Colino, J. L. Sacedon, L. Del Olmo, and J. L. Vincent

J. Vac. Sci. Technol. A 8, 4021 (1990); http://dx.doi.org/10.1116/1.576439 (5 pages) | Cited 4 times

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Auger electron spectroscopy depth profiles from different surfaces of the YBa2Cu3O7−x polycristalline compound, such as fracture and polished fracture surface of sintered ceramics, fracture of isostatically pressed powder and powder surface, have been measured. For the first time in this material, a study of the apparent enrichments in the Auger profiles compared with a preferential sputtering model in nonsimple oxides, recently tested in other perovskite oxide compound, is reported. These data show an oxygen surface release and an intergrain copper enrichment as consequence of thermal processing of the material. Thus, the existence of different stoichiometry in the grain boundaries as an additional contribution to the formation of weak links appears confirmed.
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74.70.-b Superconducting materials other than cuprates
62.20.M- Structural failure of materials
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Auger and x‐ray electron spectroscopy studies of hBN, cBN, and N+2 ion irradiation of boron and boron nitride

R. Trehan, Y. Lifshitz, and J. W. Rabalais

J. Vac. Sci. Technol. A 8, 4026 (1990); http://dx.doi.org/10.1116/1.576471 (7 pages) | Cited 27 times

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Boron and nitrogen KVV Auger electron spectroscopy (AES) and core level x‐ray photoelectron spectroscopy (XPS) features are shown to be conspicuously different for the cubic and hexagonal phases of boron nitride, i.e., cBN and hBN, respectively. The origin and assignments of these features are discussed in terms of the valence band density of states and plasmon losses. Application of these results to the identification of the boron nitride phase formed by N+2 irradiation of boron and N+2 or Ar+ irradiation of cubic boron nitride are presented.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.55.Nq Composition and phase identification

Principal component analysis with integral Auger electron spectroscopy spectra

N. H. Turner, J. H. Wandass, and F. L. Hutson

J. Vac. Sci. Technol. A 8, 4033 (1990); http://dx.doi.org/10.1116/1.576472 (6 pages)

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In this study, N(E) Auger electron spectroscopy (AES) depth profiles were obtained in the same determination for both the M2,3VV and LMM regions of Cu ion implanted in a 50–50 Co/Ni alloy. Principal component analysis (PCA) calculations on the M2,3 VV depth profile spectra suggested the presence of an additional component. The amount of Cu was estimated at about the detection limit in the M2,3VV depth profile when an averaged Co‐Ni standard was used from the end of profile. This depth profile was similar to that obtained in an earlier study with derivative AES spectra. Simulated M2,3VV spectra (with added noise) for the ion implanted alloy indicated that Cu should be detected at a relative amount of 2 at. %. The number of components indicated by PCA in the integral LMM depth profile was the same as the number of standards employed. Again, the depth profile from the integral LMM spectra was similar to that obtained from the derivative spectra; in both cases the relative atomic amount of Cu was about three times that determined in the M2,3VV spectral region. Thus, preferential sputtering of Cu seems to be present and PCA could detect this effect. In addition, Co appeared to be preferentially sputtered compared to Ni. PCA analysis was not successful when loss features were removed (which cannot be done easily with derivative AES spectra) from both the M2,3VV and LMM spectra.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Determination of H, C, N, and O in indium phosphide by secondary‐ion mass spectrometry

M. Gauneau, R. Chaplain, A. Rupert, M. Salvi, and B. Descouts

J. Vac. Sci. Technol. A 8, 4039 (1990); http://dx.doi.org/10.1116/1.576473 (7 pages) | Cited 1 time

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Hydrogen, carbon, nitrogen, and oxygen are electrical active elements in III–V compounds and the knowledge of their concentrations in these materials is of primary importance. The secondary‐ion mass spectrometry (SIMS), under cesium bombardment and negative secondary‐ion collection, is probably the most powerful technique which has been developed to address this problem because it enables quantitative analyses with good lateral and depth resolutions to be made. Recent investigations using SIMS have shown that the detection limits of gaseous species are limited by the redeposition of vacuum contaminant molecules onto the sample surfaces, or by the ionization of these molecules in the gas phase. As a consequence, these limits critically depend on the experimental conditions, i.e., they are differently dependent on the etching rate: they decrease more steeply when reducing the raster‐scanned area for a fixed primary current than when decreasing the primary current for a fixed eroded area. The previous experiments were performed in GaAs, mainly for carbon and oxygen. This paper describes similar investigations for H, C, N, and O in InP. H, C, N, and O were implanted to the same dose (1015 cm−2) at different energies so as to obtain maximum distributions at about 700 nm. The depth profiles of the respective elements were monitored and quantified for three primary beam currents (25, 50, and 100 nA) raster scanned, in turn, over three different areas (75, 50, and 25 μm2). The detection limits were deduced from the background levels without any substraction. The best values were 1–1.5×1016, 1×1016, 5–7×1014, and 5–7×1015 cm−3 for H, C, N, and O, respectively. The low limit measured for nitrogen was obtained by monitoring 31P2N− clusters. Such molecular ions are revealed to exhibit high ionization probabilities and they could be recommended to improve the sensitivity. The technique which consists in rastering moderate primary currents over small areas results in a compromise between low detection limits and sharp depth resolutions, but it will be shown that relatively low detection limits are attainable at low erosion rates by decreasing only the primary current.
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61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

X‐ray photoelectron and mass spectroscopic study of electron irradiation and thermal stability of polytetrafluoroethylene

Donald R. Wheeler and Stephen V. Pepper

J. Vac. Sci. Technol. A 8, 4046 (1990); http://dx.doi.org/10.1116/1.576474 (11 pages)

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Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 °C. The behavior of the material as a function of radiation dose and temperature was studied by x‐ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. A quantitative comparison of the radiation dose rate with that in other reported studies showed that, for a given total dose, the damage observed by XPS is greater for higher dose rates. Lightly damaged material heated to 300 °C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS that were associated with damage diminished, giving the appearance that the radiation damage annealed. The observations were interpreted by incorporating mass transport of severed chain fragments and thermal decomposition of severely damaged material into the branched and cross‐linked network model of irradiated PTFE. The apparent annealing of the radiation damage was due to covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.
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61.80.Fe Electron and positron radiation effects
81.40.Gh Other heat and thermomechanical treatments
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Electron excited M‐region resonant x‐ray excitation spectra from cerium and oxidized cerium

Bryan E. Mason and Robert J. Liefeld

J. Vac. Sci. Technol. A 8, 4057 (1990); http://dx.doi.org/10.1116/1.576475 (4 pages)

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Electron excited M‐region x‐ray resonances in cerium and cerium oxide were investigated with an instrument which permits simultaneous recording of x‐ray emissions and electron spectra from samples prepared in an ultrahigh vacuum. X‐ray intensities were recorded as a function of incident electron energy from 850 to 930 eV. This range encompasses the binding energies of the M5 and M4 shell electrons in cerium and the associated x‐ray continuum resonances. The x‐ray excitation spectra obtained in this study show large resonances for incident electron energies near the M5 and M4 shell ionization energies, but the electron spectra show no corresponding features. The spectra of resonant x rays from cerium oxide show almost no ‘‘chemical shift’’ relative to those from the pure metal but exhibit large increases in the intensity of the resonances. No explanation as to why the oxidized sample x‐ray yields are higher is offered. An estimate of the maximum x‐ray photon yield per incident electron for cerium and cerium oxide via the resonance effect is 2×10−6 (M5 ) and 9×10−7 (M4 ) for cerium and 6×10−6 (M5 ) and 4×10−6 (M4 ) for cerium oxide.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.85.-m X- and γ-ray instruments

Low‐energy electron diffraction observations of the thermal evolution of 0.5–3.0 ML Pt/Ni(111)

John A. Barnard and Jean Jacques Ehrhardt

J. Vac. Sci. Technol. A 8, 4061 (1990); http://dx.doi.org/10.1116/1.576440 (8 pages) | Cited 9 times

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The near‐surface geometric structure of the system 0.5–3.0 ML Pt/Ni(111) has been monitored with low‐energy electron diffraction (LEED) as a function of annealing treatment. In this coverage range a variety of structures are documented. Evidence is presented for commensurate submonolayer Pt (despite the large misfit) and incommensurate (but aligned) second and third layer Pt, at low temperatures. The second and third layers of Pt yield (111)‐type LEED patterns but with spacing at an intermediate value between Ni(111) and Pt(111). In a very narrow range of coverage and annealing treatment (1.5–2 ML PT and 673–773 K) a hexagonal satellite appears around each primary beam. These satellites are interpreted as evidence for partially rotated incommensurate second layer Pt domains. Annealing at 873 K or above of even the thickest deposits (3 ML) produces diffraction spots indistinguishable from Ni(111). Structural evidence is correlated with the thermal evolution of the surface electronic structure in the same system (using photoemission for local and macroscopic work function measurements). The photoemission results complement the LEED information and together they provide evidence for complex diffusional rearrangements even at low temperatures in this system.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
73.20.At Surface states, band structure, electron density of states
68.35.B- Structure of clean surfaces (and surface reconstruction)

Modifications in the interfacial reaction between thin films of Ti and Al due to alloying the Al with Si

M. Ben‐Tzur, R. Fastow, M. Eizenberg, J. Rosenberg, and M. Frenkel

J. Vac. Sci. Technol. A 8, 4069 (1990); http://dx.doi.org/10.1116/1.576441 (5 pages)

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The interfacial reaction between Al(Si) and Ti thin films has been studied and compared to that for pure Al and Ti. The experimental techniques employed were Rutherford backscattering spectrometry, transmission electron microscopy, and measurements of the sheet resistivity. It has been found that alloying the Al with Si delays the onset temperature for Al3Ti formation (430 °C for 1% Si compared to 300 °C for pure Al), decreases significantly the reaction rate, and causes a nonuniform and nonplanar interaction. The effects of the Si concentration and the annealing environment have also been studied. A model based on processes which impede the transport of Ti atoms to the reaction front can explain the obtained results.
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68.35.Fx Diffusion; interface formation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
85.40.Ls Metallization, contacts, interconnects; device isolation

Studies of the interface between the epoxy molding compound and the copper leadframe by x‐ray photoelectron spectroscopy, Auger electron spectroscopy, and secondary electron microscopy

F. M. Pan, S. R. Horng, T. D. Yang, and V. Tang

J. Vac. Sci. Technol. A 8, 4074 (1990); http://dx.doi.org/10.1116/1.576442 (5 pages) | Cited 5 times

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The interface between the epoxy molding compound and the copper leadframe of an integrated circuit device has been studied by x‐ray photoemission spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary electron microscopy (SEM). The surface of the copper frame is composed of CuO, Cu2 O, or Cu(OH)2 depending on the heat treatment for the frame before the molding process. The XPS results show that cuprous oxide is the primary copper oxide at the interface between the leadframe and the epoxy polymeric encapsulant after the molding process. Copper was found to migrate into the epoxy resin side. According to AES and SEM, silica fillers in the molding compound abrade the copper oxide layer on the copper frame during the molding process, and the injected hot epoxy fluid can interact directly with the freshly exposed metallic copper surface. The accelerator of the molding compound segregates to the abraded area at the interface. The rugged interfacial structure close to the molding compound injection gate is probably the primary factor causing the microgap problem at the interface.
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85.40.Ls Metallization, contacts, interconnects; device isolation
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Stabilization techniques for spinning rotor gage residual drag

Suk‐Ho Choi, Sharrill Dittmann, and Charles R. Tilford

J. Vac. Sci. Technol. A 8, 4079 (1990); http://dx.doi.org/10.1116/1.576443 (7 pages)

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The pressure‐independent residual drag on a spinning ball requires an offset correction for the accurate use of a spinning rotor vacuum gage (SRG) at low pressures. Instabilities in the residual drag (RD) can cause significant errors in low‐pressure SRG measurements. The instabilities usually occur as discontinuous shifts when a ball is levitated by the magnetic suspension, or as continuous changes as the ball slows down. The discontinuous shifts in residual drag have been found to be caused by changes in the orientation of the ball’s magnetic moment, induced by the suspension field or the inductive drive circuit. Premagnetizing the ball in a strong field has stabilized the orientation of the magnetic moment and the RD value. The continuous changes are caused by competition between magnetic and inertial forces, which result in a frequency‐dependent orientation of the rotational axis of the ball. Etching a spot on the ball alters its shape and defines an inertial axis. Magnetizing the ball in a preferred direction with respect to this axis minimizes both the residual drag and its frequency dependence.
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07.30.Dz Vacuum gauges

A study of the linearity of transfer leaks and a helium leak detector

C. D. Ehrlich, S. A. Tison, H. Y. Hsiao, and D. B. Ward

J. Vac. Sci. Technol. A 8, 4086 (1990); http://dx.doi.org/10.1116/1.576444 (6 pages) | Cited 2 times

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A study has been performed of the linearity of two types of variable‐reservoir‐pressure leaks and a commercial tuned magnetic sector mass‐spectrometer helium leak detector. While the leaks exhibit predictable (but not always linear) behavior over a broad range, the linearity of the leak detector depends strongly on properly correcting for observed drift and random fluctuations in the measured leak rate.
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07.30.Hd Vacuum testing methods; leak detectors

Reduction of particle contamination by controlled venting and pumping of vacuum loadlocks

G. Strasser, H. P. Bader, and M. E. Bader

J. Vac. Sci. Technol. A 8, 4092 (1990); http://dx.doi.org/10.1116/1.576445 (6 pages) | Cited 2 times

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The control of particle and chemical contamination is one of the main challenges on the way to ever higher integration in the production of advanced semiconductor devices. Inadequate pumping and venting of vacuum equipment loadlocks has been identified as a major cause for particle contamination. To overcome the problem, ‘‘soft pumping’’ and ‘‘soft venting’’ procedures are in use. A quantitative assessment of the term ‘‘soft’’ has as yet been missing. We have used standard particle monitoring equipment like a Climet 6300 airborne particle counter and a Tencor 5000 surface particle counter to quantify the contamination level after different venting and pumping procedures. In contrast to a widespread belief we found that the resuspension of sub‐micrometer particles does not start at the transition point from laminar to turbulent flow conditions but above. Most particles are generated at low pressure in the initial phase of venting. To account for the experimental effects observed, a theoretical model was developed. Using optimized pumping and venting procedures, airborne particle levels below class 10 were obtained in equipment loadlocks. A surface particle density increase below 10−3 cm−2 for particles larger than 0.3 μm was measured after proper venting and pumping for both vertical and horizontal oriented wafers.
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07.30.Bx Degasification, residual gas
81.65.-b Surface treatments

Ultrahigh vacuum precise positioning device utilizing rapid deformations of piezoelectric elements

Y. Yamagata, T. Higuchi, H. Saeki, and H. Ishimaru

J. Vac. Sci. Technol. A 8, 4098 (1990); http://dx.doi.org/10.1116/1.576446 (3 pages) | Cited 5 times

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Recently precise positioning devices with low outgassing rates have been required for production systems of very large scale integrated circuits, surface analysis systems, and scanning tunneling microscopes in ultrahigh vacuum. A bakable XYθ three‐axis positioning table using a unique positioning mechanism utilizing friction and inertial forces caused by rapid deformations of piezoelectric elements was developed. The table has a hexagonal shape of 120 mm in diameter and is mainly made of aluminum alloys with an EX‐process. The table has three feet with an Si3N4 ball on each bottom side and set on a plate made of Pyrex glass. The table was able to operate in an ultrahigh vacuum environment of the order of 10−12 Torr.
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06.60.Sx Positioning and alignment; manipulating, remote handling
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
77.65.-j Piezoelectricity and electromechanical effects

High resolution secondary ion mass spectrometry depth profiling using continuous sample rotation and its application to superlattice and delta‐doped sample analysis

Eun‐Hee Cirlin, John J. Vajo, Thomas C. Hasenberg, and Robert J. Hauenstein

J. Vac. Sci. Technol. A 8, 4101 (1990); http://dx.doi.org/10.1116/1.576447 (3 pages) | Cited 3 times

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We report the development of secondary ion mass spectrometry (SIMS) with continuous sample rotation to achieve high resolution that is independent of depth during compositional and dopant sputter depth profiling. Sample rotation reduces the ion beam‐induced surface roughness that often limits the depth resolution in SIMS. To illustrate the effects of sample rotation on SIMS analysis, measurements both with and without rotation were performed on a molecular beam epitaxy grown AlGaAs/GaAs superlattice with 100 periods and 5‐nm‐thick layers, and a boron delta‐doped (atomically planar) Si sample, with dopant concentrations from 1016–1021 atoms/cm3 at depths of 0.5–2.0 μm.
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07.75.+h Mass spectrometers
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Ultrathin film of Bi2Sr2CuOx formed by molecular beam epitaxy using NO2

Maki Kawai, Shunji Watanabe, and Takashi Hanada

J. Vac. Sci. Technol. A 8, 4104 (1990); http://dx.doi.org/10.1116/1.576448 (2 pages) | Cited 3 times

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Abstract Unavailable
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Bx Metals, semimetals, and alloys
68.55.-a Thin film structure and morphology
73.20.At Surface states, band structure, electron density of states

Comment on ‘‘Influences of noble gases (Ne, Ar, and Kr) on magnetic properties of ion‐beam sputtered Fe/SiO2 multilayer films’’

E. Paparazzo

J. Vac. Sci. Technol. A 8, 4106 (1990); http://dx.doi.org/10.1116/1.576449 (2 pages)

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This paper reports some comments on the x‐ray photoelectron spectra of ion beam sputtered Fe/SiO2 multilayer films which were discussed in a recent work by Senda and Nagai [J. Vac. Sci. Technol. A 8, 13 (1990)]. The area of major disagreement regards the interpretation that the two authors gave to explain the Si2p and O1s spectra. It is pointed out that great care should be exercized in order to account for the Ar ion reductive effects in iron–silicon oxide systems, and that a careful analysis should be done of the complex O1s spectra in order to assess which oxidized species are present in the films.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Cd Deposition by sputtering

Highly porous and electrically insulating films deposited by reactive physical vapor deposition

Walter Lang

J. Vac. Sci. Technol. A 8, 4108 (1990); http://dx.doi.org/10.1116/1.576450 (3 pages) | Cited 1 time

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Highly porous metallic films can be deposited by a modified physical vapor deposition process. The deposition of those films is investigated for several metals. For application in infrared optics and sensors it is often necessary to deposit a highly porous and electrically insulating film. This type of film can be produced by reactive physical vapor deposition of aluminum in a low‐pressure O2/Ar atmosphere.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Can Auger spectra vary with change of the beam‐sample‐analyzer assembly geometry?

R. Siuda

J. Vac. Sci. Technol. A 8, 4111 (1990); http://dx.doi.org/10.1116/1.576451 (3 pages)

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Abstract Unavailable
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

The effect of cathodic hydrogen charging of substoichiometric Ni3Al on Auger electron spectroscopy measured intergranular boron segregation

Ashok Choudhury, C. L. White, and C. R. Brooks

J. Vac. Sci. Technol. A 8, 4114 (1990); http://dx.doi.org/10.1116/1.576452 (3 pages)

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A cathodic hydrogen charging procedure is described which allows intergranular fracture in boron‐doped Ni3 Al samples which are normally ductile and do not fracture intergranularly. This has allowed determination of the boron content of the grain boundaries. It is shown that the hydrogen charging has no influence on the measured boron content.
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81.40.Lm Deformation, plasticity, and creep
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.05.Bx Metals, semimetals, and alloys

A simple ultrahigh vacuum surface magneto‐optic Kerr effect setup for the study of surface magnetic anisotropy

J.‐P. Qian and G.‐C. Wang

J. Vac. Sci. Technol. A 8, 4117 (1990); http://dx.doi.org/10.1116/1.576453 (3 pages) | Cited 11 times

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We describe a unique in situ rotatable electromagnet which utilizes only one set of coils. The magnetic field produced by the electromagnet can be aligned either parallel or perpendicular to the plane of a sample.These two magnetized fields allow one to study the surface magnetic anisotropy of ultrathin ferromagnetic films through the measurement of surface hysteresis loops.
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75.70.Rf Surface magnetism
78.66.Bz Metals and metallic alloys
07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices
75.50.Bb Fe and its alloys
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