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Nov 1993

Volume 11, Issue 6, pp. 2883-3142


Multiple steady states in electron cyclotron resonance plasma reactors

Eray S. Aydil, Jeffrey A. Gregus, and Richard A. Gottscho

J. Vac. Sci. Technol. A 11, 2883 (1993); http://dx.doi.org/10.1116/1.578663 (10 pages) | Cited 22 times

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Although electron cyclotron resonance (ECR) plasma reactors are being used in the microelectronics industry for etching and deposition of thin films they are prone to instabilities that can wreak havoc with manufacturing processes. Plasma conditions are often unstable because of nonlinear coupling between wave propagation, power absorption, neutral density, and charge density profiles. We report on hysteresis, multiple steady states and abrupt transitions in an ECR plasma reactor that can alter the plasma properties drastically. Substrate platen floating potential and Langmuir probe measurements are used to identify several abrupt transitions and regions in the operating parameter space where the plasma can exist in either one of two different states under identical operating conditions (microwave power, pressure, flow rate, magnetic field, rf bias etc.) Depending on how the plasma is started either branch can be obtained. Abrupt transitions and hysteresis in plasma properties are observed both with and without rf bias under typical conditions used in plasma processes. Such transitions can cause drastic deviations in plasma parameters—density, current, uniformity—and may result in degraded process characteristics—uniformity, rate, selectivity, linewidth control. Statistical techniques used to design and develop processes cannot properly account for discontinuous changes in the state of the plasma and can produce brittle processes that can suddenly lead to catastrophic failure. Care must be taken to map out the regions of bistability for the purpose of avoiding them or controlling the plasma in these regions. While the mechanism responsible for the multiple steady states and abrupt transitions reported here is not well understood, it is clear that these phenomena depend critically on the neutral density.
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52.50.Dg Plasma sources

Study of the effect of a probe on the plasma in the source region of an electron cyclotron resonance discharge

M. D. Bowden, F. Kimura, H. Muta, K. Uchino, K. Muraoka, and M. Maeda

J. Vac. Sci. Technol. A 11, 2893 (1993); http://dx.doi.org/10.1116/1.578664 (4 pages) | Cited 2 times

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Langmuir probes are commonly used to measure electron density and temperature in the low temperature and low density plasmas used in plasma processing, although the plasma conditions are sometimes not ideal for such measurements. We report measurements of the perturbing effect of such probes in the high magnetic field region of an electron cyclotron resonance discharge by making Thomson scattering measurements of electron temperature and density under normal operating conditions and also in the presence of a probe. The results revealed that the probe clearly qualitatively changed the plasma. An attempt to quantify this change appeared to indicate that the effect of the probe was to decrease the electron density and increase the electron temperature in the vicinity of the probe.
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52.70.Ds Electric and magnetic measurements
52.20.Fs Electron collisions

Effects of substrate bias frequency in an electron cyclotron resonance plasma reactor

J. B. O. Caughman and W. M. Holber

J. Vac. Sci. Technol. A 11, 2897 (1993); http://dx.doi.org/10.1116/1.578665 (6 pages) | Cited 2 times

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The effects of varying the substrate bias frequency on both substrate and plasma parameters have been studied in an electron cyclotron resonance plasma reactor. The frequency was varied between 13.56 and 76.0 MHz. The plasma density at the substrate was in the mid‐1011/cm3 range. It was generally found that as the frequency was increased, less rf power was coupled to the ions accelerated across the sheath to the substrate, and more rf power was coupled to the plasma bulk. Thus, more power was needed to achieve the same self‐bias voltage as the bias frequency was raised. The same trend was seen as the plasma density increased—i.e., more rf power was needed to achieve the desired self‐bias voltage at higher densities. These effects are analyzed in terms of a simple sheath model of the reactor.
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52.75.-d Plasma devices

Copper deposition by electron cyclotron resonance plasma

W. M. Holber, J. S. Logan, H. J. Grabarz, J. T. C. Yeh, J. B. O. Caughman, A. Sugerman, and F. E. Turene

J. Vac. Sci. Technol. A 11, 2903 (1993); http://dx.doi.org/10.1116/1.578666 (8 pages) | Cited 31 times

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An electron cyclotron resonance plasma reactor has been built in order to study the filling of high aspect‐ratio features on semiconductor devices with metal. The reactor produces a plasma of copper which is nearly 100% ionized at the substrate, without the use of any buffer or carrier gas. The ion flux is dependent on both the feed rate of copper neutrals into the plasma region, and on the microwave power absorbed in the plasma. Solid filling of features having aspect ratios as high as 4.2 is demonstrated, and a simple model is derived to explain the fill characteristics.
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85.40.Ls Metallization, contacts, interconnects; device isolation

Direct current bias as an ion current monitor in the transformer coupled plasma etcher

Yunju Ra and Ching‐Hwa Chen

J. Vac. Sci. Technol. A 11, 2911 (1993); http://dx.doi.org/10.1116/1.578667 (3 pages) | Cited 14 times

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Independent of plasma generation, ion energy can be controlled by applying rf power to a substrate in the transformer coupled plasma etcher. Due to high plasma density of the plasma source, most of rf power to the substrate is confined within the sheath region and used in accelerating ions. This enables development of a simple equation correlating dc bias and ion current density. Based on this equation, ion current densities for different plasma conditions have been measured. The results show good agreement with Langmuir probe measurements.
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52.75.-d Plasma devices
52.70.Ds Electric and magnetic measurements

Photo‐enhanced chemical vapor deposition: System design considerations

S. Lian, B. Fowler, S. Krishnan, L. Jung, C. Li, I. Manna, D. Samara, and S. Banerjee

J. Vac. Sci. Technol. A 11, 2914 (1993); http://dx.doi.org/10.1116/1.578668 (10 pages) | Cited 1 time

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ArF excimer laser‐enhanced photochemical vapor deposition of Si from Si2H6 in an UHV deposition chamber has been used to achieve Si epitaxy at temperatures as low as 250 °C. The system design criteria are discussed. Modified Schimmel etching/Nomarski microscopy, transmission electron microscopy, and reflection high energy electron diffraction have been used to study the microstructure of Si films as a function of laser power, substrate temperature and disilane partial pressure. The growth rates were observed to be linearly dependent on laser intensity and Si2H6 partial pressure. The morphology of the films is excellent and defects such as dislocation loops and stacking faults are not seen.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology

Reaction pathways for ArF excimer laser assisted tungsten chemical vapor deposition from a WF6–H2 gas mixture

P. Heszler, J. O. Carlsson, and P. Mogyorósi

J. Vac. Sci. Technol. A 11, 2924 (1993); http://dx.doi.org/10.1116/1.578669 (7 pages) | Cited 4 times

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Photolytic tungsten chemical vapor deposition by an ArF excimer laser from a WF6/H2/Ar gas mixture is a very complicated process with reactions occurring both in series and in parallel. In this article different reaction pathways were modeled and compared with experimental deposition rate data. The absorption cross section for WF6 was measured to 1.7×10−18 cm2 at the ArF excimer laser wavelength of 193 nm. From a rate equation model, it was concluded that the direct photolytic contribution to the deposition rate was negligible. Moreover, reduction of tungsten subfluorides by hydrogen atoms, formed in reactions between photolytically released fluorine atoms and molecular hydrogen, was also found to be negligible. However, photolysis in combination with various radical reactions generate a relatively high concentration of tungsten subfluorides (WF3, WF4, and WF5). Thermochemical calculations indicate that H2 reduction of tungsten subfluorides to solid tungsten, forming clusters in the vapor, is highly probable. Among the different cluster nucleation mechanisms polymerization of tungsten subfluorides seems to be an important step. This also explains the influence of WF6 partial pressure on the deposition rate.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Laser‐assisted chemical vapor deposition of InN on Si(100)

Y. Bu, L. Ma, and M. C. Lin

J. Vac. Sci. Technol. A 11, 2931 (1993); http://dx.doi.org/10.1116/1.578670 (7 pages) | Cited 11 times

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Laser‐assisted chemical vapor deposition of InN on Si(100) using HN3 and trimethyl indium (TMIn) with and without 308‐nm photon excitation has been studied with x‐ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and scanning electron microscopy (SEM). Without 308‐nm excimer laser irradiation, no InN film was built on the surface under the present low‐pressure conditions. When the photon beam was introduced, InN films with In:N atomic ratio of 1.0±0.1 and a thickness of more than 20 Å (the limit of the electron escaping depth for the In 3d x‐ray photoelectrons) were formed at temperatures of 300–700 K. The He ii UP spectra taken from these InN films agree well with the result of a pseudopotential calculation for the InN valence band. Our XPS measurements indicate a three‐dimensional (3D) island growth of InN on Si(100) at 700 K, which is confirmed by the SEM images. Although the SEM images taken from the same samples with 2000 × magnification showed very smooth InN films, InN islands of about 100 nm in diameter could be clearly observed with a magnification of ≥20 000×. In contrast, the InN film grown at 300 K showed valleys of uncovered substrate instead of InN islands. These uncovered substrate areas, corresponding to about 5% of the surface exposed to the probing x‐ray radiation, probably result from incomplete decomposition of In–C bonds and poor diffusion kinetics at this temperature. Above 800 K, dissociation and desorption of In‐ and N‐ containing species occurred and thus no InN film was formed on the surface.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Influence of ion beam modification on the oxidation behavior of intermetallic compound Ni3Al(0.1B)

Xianghuai Liu, Zhihong Zheng, Wei Huang, Zixin Lin, Xi Wang, Genqing Yang, Shichang Zou, S. Taniguchi, and T. Shibata

J. Vac. Sci. Technol. A 11, 2938 (1993); http://dx.doi.org/10.1116/1.578671 (3 pages)

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Ion implantation, ion beam mixing, and ion beam enhanced deposition (IBED) were employed to improve oxidation resistance of intermetallic compound Ni3Al(0.1B) in pure flowing oxygen at temperature of 1100 K. X‐ray diffraction and scanning electron microscopy were used to examine the composition and structure of the scales after oxidation. Improved resistance to oxidation of Ni3Al(0.1B) was observed in Ta+‐implanted, ion beam mixed Si layers, and IBED films coated specimens. The possible mechanisms for these effects were discussed.
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81.05.Bx Metals, semimetals, and alloys
61.72.up Other materials

Effects of O2, air, and CF4 plasmas on poly(etherketone) surfaces

E. C. Onyiriuka

J. Vac. Sci. Technol. A 11, 2941 (1993); http://dx.doi.org/10.1116/1.578672 (4 pages) | Cited 2 times

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The effects of molecular oxygen, air, and CF4 plasma treatments on the surface chemistry of poly(etherketone) have been studied by x‐ray photoelectron spectroscopy. Oxygen or ambient air plasma treatment led to oxidation producing mainly surface ether, and carbonyl groups. The reaction with CF4 plasma resulted primarily in the formation of surface carbonates, CF2–CF2, and CF3 with CF2–CF2 as the dominant species. For the reaction with CF4 plasma, the experimental data indicated that cleavage of the polymer aromatic structure is extensive.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

High quality, high deposition rate SiO2 films at low temperatures using silicon fluorides and plasma assisted deposition techniques

C. Falcony, J. C. Alonso, A. Ortiz, M. Garcia, E. P. Zironi, and J. Rickards

J. Vac. Sci. Technol. A 11, 2945 (1993); http://dx.doi.org/10.1116/1.578673 (5 pages) | Cited 4 times

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High quality SiO2 films have been deposited by the plasma enhanced chemical vapor deposition technique using SiF4 and N2O. It has been determined that a small amount of hydrogen is needed to reduce the amount of residual fluorine atoms in the oxide improving the structural and electrical properties of the film. Using SiH4 as a source of hydrogen instead of H2 results in a high deposition rate increasing from 7 to more than 500 A/min depending on the total content of SiH4. However, for the high deposition rates studied, hydrogen related impurities start to appear and some degradation of the electrical characteristics of the films are observed.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Growth kinetics of Si hemispherical grains on clean amorphous‐Si surfaces

Akira Sakai, Toru Tatsumi, and Koichi Ishida

J. Vac. Sci. Technol. A 11, 2950 (1993); http://dx.doi.org/10.1116/1.578674 (4 pages) | Cited 7 times

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In solid‐phase growth on SiO2 layers of amorphous‐Si (a‐Si) having clean, native oxide‐free surfaces under ultrahigh vacuum conditions, a novel mode of crystallization can be observed: upward growth of Si grains resulting in the formation of nearly hemispherical‐shaped grains protruding from the flat surface. Kinetics of the grain growth has been studied by measuring the annealing time and temperature dependence of the hemispherical grain size. The growth behavior is well explained by a model based on the crystallization of surface diffusive atoms supplied only from where the edge of the hemispherical grain contacts the a‐Si surface. The activation energy for hemispherical grain growth was found to be 2.3±0.1 eV from the temperature dependence of the flux density, defined as the number of atoms crystallized per unit time per unit surface area enclosed by the edge. The atomistic mechanism for the hemispherical shape formation and the origin of the activation energy are also discussed.
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81.05.Rm Porous materials; granular materials

Characterization of silicon dioxide films deposited at low pressure and temperature in a helicon diffusion reactor

C. Charles, G. Giroult‐Matlakowski, R. W. Boswell, A. Goullet, G. Turban, and C. Cardinaud

J. Vac. Sci. Technol. A 11, 2954 (1993); http://dx.doi.org/10.1116/1.578675 (10 pages) | Cited 19 times

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Silicon dioxide films have been deposited at low pressure (a few millitorr) and low substrate temperature (<200 °C) by oxygen/silane helicon diffusion radio frequency plasmas. High deposition rates (20–80 nm/min) are achieved at 800 W rf source power. The effect of the oxygen/silane flow rate ratio (R) on the film properties has been investigated: characterization of the deposited films has been carried out by in situ ellipsometry, ex situ Fourier transform infrared spectroscopy, Rutherford backscattering, x‐ray photoelectron spectroscopy (XPS), and chemical etch rate measurements (P etch) and the results have been compared to thermally grown oxide. The deposition kinetics has a great effect on the internal film structure: for films presenting a good stoichiometry ([O]/[Si]≥1.95 for R≥3), a decrease in the deposition rate is accompanied by a decrease of the refractive index, P‐etch rate and XPS line width and by an increase of the Si–O stretching peak frequency toward the thermal oxide respective values. A sufficient oxygen/silane flow rate ratio (R=10) leads to stoichiometric films which exhibit good optical properties. Small differences in the P‐etch rate, XPS linewidth, and infrared stretching peak frequency are still observed between our stoichiometric plasma deposited film and a thermally grown oxide film.  
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Nq Composition and phase identification
68.55.-a Thin film structure and morphology

Structure and tribology of hard carbon films synthesized by ion beam deposition

Xiaoming He, Wenzhi Li, and Hengde Li

J. Vac. Sci. Technol. A 11, 2964 (1993); http://dx.doi.org/10.1116/1.578676 (6 pages) | Cited 4 times

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Hard carbon films were formed on Si(111) wafer and AISI 52100 steel by CHn+ ion beam deposition with energies varied from 200 eV to 15 keV. The effects of bombarding energy of CHn+ on the bonding structure and hardness of carbon films were investigated. The films were revealed to consist of amorphous carbon with the structure of mixed sp3+sp2 bonding. However, it was showed that carbon films prepared under bombarding energy of 200–550 eV were much similar to diamond in the valence band structure and had more sp3 bonds. The friction and wear properties of films deposited on AISI 52100 steel were also detected and the experimental results indicated that as wear load was less or equal to 15 N, the normal wear process can steadily last with a friction coefficient of 0.1–0.15. In addition, hard carbon films were suggested to possess the self‐lubricating function and good impact‐resistance to enhance their antiwearing ability.
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81.40.Pq Friction, lubrication, and wear
68.60.Bs Mechanical and acoustical properties

Relationship of crystallographic orientation and impurities to stress, resistivity, and morphology for sputtered copper films

Andrew F. Burnett and Jay M. Cech

J. Vac. Sci. Technol. A 11, 2970 (1993); http://dx.doi.org/10.1116/1.578677 (5 pages) | Cited 12 times

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Copper has 44% higher conductivity than aluminum, making copper an attractive interconnect metal for advanced multilevel interconnections in integrated circuits (IC) and multichip modules (MCM). Since sputter deposition is widely used in IC and MCM fabrication, the properties of sputtered copper films are investigated in this study. In particular, MCM technology requires relatively thick coatings (5–8 μm), which can result in high stress. Thin film stress can lead to dielectric cracking, wafer bow, and reduced operating lifetime. This study reports the residual stress, morphology, and electrical resistivity of annealed copper coatings as a function of the thin film crystal orientation determined by x‐ray diffraction. We found that the stress and electrical resistivity of copper thin films can be significantly reduced by controlling the orientation of the copper crystallites.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
73.61.At Metal and metallic alloys
85.40.Ls Metallization, contacts, interconnects; device isolation

Highly transparent and conductive group IV impurity‐doped ZnO thin films prepared by radio frequency magnetron sputtering

Hirotoshi Sato, Tadatsugu Minami, and Shinzo Takata

J. Vac. Sci. Technol. A 11, 2975 (1993); http://dx.doi.org/10.1116/1.578678 (5 pages) | Cited 7 times

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Highly transparent and conducting group IV impurity‐doped ZnO thin films have been prepared on low‐temperature substrates below 140 °C by rf magnetron sputtering. Resistivities of 4–8×10−4 Ω cm and an average transmittance above 85% in the visible range were obtained for ZnO films doped with Si, Ge, Ti, Zr, or Hf. The stability of resistivity for use in high‐temperature atmospheres was significantly improved by the impurity doping. On the contrary, the resistivity of ZnO films doped with Sn or Pb was higher than that of an undoped ZnO film, and these films were discolored.
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73.61.Ga II-VI semiconductors
81.15.Cd Deposition by sputtering
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Sustained self‐sputtering using a direct current magnetron source

Witold M. Posadowski and Zbigniew J. Radzimski

J. Vac. Sci. Technol. A 11, 2980 (1993); http://dx.doi.org/10.1116/1.578679 (5 pages) | Cited 21 times

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Sustained self‐sputtering of copper and silver targets has been achieved using a direct current magnetron source. The sputtering was carried out successfully without an inert gas at 8×10−6 Torr. A very high deposition rate was obtained in this mode of operation. The possible mechanism and requirements for sustained self‐sputtering are discussed and other potential material candidates are suggested.
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81.15.Cd Deposition by sputtering
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Sputter distribution of a large scale ion beam coater

N. Albertinetti and H. T. Minden

J. Vac. Sci. Technol. A 11, 2985 (1993); http://dx.doi.org/10.1116/1.578680 (4 pages)

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TiO2 was reactively sputtered in a large ion beam system from a 8 in. diam Ti target. 32 glass samples were mounted in concentric semicircles on a 12 in. diam plate, and after sputtering the thickness of the samples was measured. In other experiments TiO2–SiO2 multilayer dielectric coatings were deposited in the same system. In these cases the samples were mounted on a planetary fixture, and thickness differences were measured across a single planet. Although the gross features of the thickness distributions could be explained by almost any reasonable sputter distribution, significant details of the thickness distribution could not. To explain these differences qualitatively, texturing of the target and scattering of the sputtered atoms by the neutral Ar atoms of the sputtering gas is postulated. These effects distort the thickness distribution in a manner which is not easily predicted by theory.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

Influence of the plasma on substrate heating during low‐frequency reactive sputtering of AIN

David A. Glocker

J. Vac. Sci. Technol. A 11, 2989 (1993); http://dx.doi.org/10.1116/1.578286 (5 pages) | Cited 22 times

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Reports in the literature over the last several years have pointed out the advantages of using low‐frequency power for reactive sputtering. In the 10–100 kHz range the impedance of the poisoned target surface is low enough to prevent the charge accumulation that leads to arcing, while the problems associated with rf power are largely avoided. We have found, however, that for a variety of materials the substrate heating at these frequencies is somewhat higher than that observed during dc reactive sputtering under similar conditions. In order to quantify this, we have calorimetrically compared the incident substrate energies while reactively sputtering AlN with both dc and 35 kHz power. In both cases, the power was delivered simultaneously to two 200 cm2 targets. In one set of experiments, they were operated at a total power of 500 W, a total pressure of 10 mTorr, and a N2/Ar flow ratio of 0.18. These conditions were on the knee of the characteristic flow hysteresis curve for our system, and target voltage feedback to the reactive gas flow was used to maintain stability. The average deposition rate and substrate incident energy were 0.82 nm/s and 20.0 eV/atom, respectively, for the dc process and 0.70 nm/s and 32.8 eV/atom for the ac process. Langmuir probe measurements show that the electron energies in the ac plasmas are somewhat higher than the electron energies in comparable dc reactive AlN plasmas and the differences between the plasma and floating potentials are comparable. The ion densities in the ac plasmas we measured averaged 6.4×1016/m3, which is several times greater than the ion densities in similar dc plasmas. We attribute the increased energies and densities to target voltage spikes as the plasma reignites on each half‐cycle, causing rapid electron acceleration in the presheath region. This leads to significantly more plasma bombardment of the substrate in the ac case than in the dc case, which our estimates show can partially explain the energy flux difference.  
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81.15.Cd Deposition by sputtering

Diamond synthesis by sputtering

Morito Matsuoka, Koichi Hoshino, and Ken’ichi Ono

J. Vac. Sci. Technol. A 11, 2994 (1993); http://dx.doi.org/10.1116/1.578287 (8 pages) | Cited 1 time

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Almost single‐phase diamond films with sp3 bonds are synthesized on Si at temperatures as low as 600 °C by a triode‐assisted sputtering system with an electric mirror. The growth rate varies between 1 and 10 nm/min. The rate depends on the deposition parameters, including substrate temperature, gas pressure, He gas fraction. The diamond is found to nucleate on a double‐layered interlayer formed on the Si surface, consisting of a 3–7 nm thick granular W layer condensed on a 3–15 nm amorphous SiC layer. The structure of this interlayer arises from the preferential diffusion of C atoms into the Si substrate. The density of diamond nucleation reaches 109–1010 cm−2. This density does not depend on the pretreatment of the substrate surface. The preferential crystallite orientation occurs along the 〈111〉 or 〈110〉 directions, and is well controlled by the He fraction during sputtering.
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81.15.Cd Deposition by sputtering

Temperature control and measurement for diamond single crystals in ultrahigh vacuum

V. S. Smentkowski and J. T. Yates

J. Vac. Sci. Technol. A 11, 3002 (1993); http://dx.doi.org/10.1116/1.578288 (5 pages) | Cited 5 times

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A method for reproducibly heating diamond single crystals is described. Measurements of the actual diamond temperature are made using a pair of embedded thermocouples. Both, steady state and temperature programmed heating methods have been characterized. It is demonstrated that diamond temperatures, when estimated by measuring the temperature of the heating support, may be in error by hundreds of degrees K.
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07.20.Dt Thermometers
07.20.Ka High-temperature instrumentation; pyrometers
65.90.+i Other topics in thermal properties of condensed matter (restricted to new topics in section 65)

Material properties and tribological performance of hydrogenated sputter carbon overcoat on rigid disk

H. J. Lee, R. Zubeck, D. Hollars, J. K. Lee, M. Smallen, and A. Chao

J. Vac. Sci. Technol. A 11, 3007 (1993); http://dx.doi.org/10.1116/1.578289 (7 pages) | Cited 7 times

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The structure and material properties of hydrogenated carbon films were studied and related to their tribological performance. Hydrogenated carbon films containing a range of 15–50 at. % of hydrogen were fabricated by magnetron sputtering using a mixture of argon and hydrocarbon gases. Raman spectroscopy was used for determining the structure of the H–C films. For physical property of H–C films, resistance of the film was measured. Nanohardness and elastic modulus of thin H–C films were also studied by measuring the load and displacement curve. The nanohardness and elastic modulus of H–C films were found to be very close to those of diamondlike carbon films fabricated by chemical vapor deposition. The stresses of H–C films were obtained by measuring the substrate curvature before and after deposition. Thermal expansion coefficients of the H–C films were obtained by measuring the change of stress of H–C film deposited on two known substrates as a function of temperature. The accelerated drag and contact start stop tests of H–C films were performed in various gas environments and it was found that the best tribological performance was obtained from the H–C overcoat with the highest hydrogen concentration.
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68.60.Bs Mechanical and acoustical properties
81.40.Pq Friction, lubrication, and wear

Deposition system for the synthesis of modulated, ultrathin‐film composites

Loreli Fister, Xiao‐Mei Li, John McConnell, Thomas Novet, and David C. Johnson

J. Vac. Sci. Technol. A 11, 3014 (1993); http://dx.doi.org/10.1116/1.578290 (6 pages) | Cited 8 times

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We have initiated a program using elemental superlattices as probes of the early stages of solid‐state reactions. The main advantage of using superlattices as reactants is the ability to tailor their structure on an angstrom length scale to control reaction kinetics. Consequently, we designed and constructed a computer‐controlled and monitored ultrahigh‐vacuum chamber for the preparation of elemental superlattices. This system is capable of manufacturing three sets of three samples in one evacuation cycle. Up to six different elements can be incorporated into each sample. Elements can be deposited from independently controlled electron‐beam sources, Knudsen, or evaporation cells. The sample drive mechanism combined with source shutters and computer control permit complex layer‐repeat units within the composite. Layer thicknesses can be controllably varied from 4 Å upward. Various attributes of the chamber include its modular design, multiple layer thickness control options, reproducibility and quality of samples, flexibility, and extensive computer monitoring during sample preparation.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

In situ substrate temperature measurement in high‐Tc superconducting film deposition

B. I. Choi, Alfredo C. Anderson, A. C. Westerheim, and M. I. Flik

J. Vac. Sci. Technol. A 11, 3020 (1993); http://dx.doi.org/10.1116/1.578291 (6 pages) | Cited 1 time

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An adaptively calibrated pyrometer (ACP) is employed to measure the substrate surface temperature during the YBa2Cu3O7−δ film growth process. The film‐thickness‐dependent emittance of the film‐substrate composite is determined from thin‐film optics for instantaneous calibration of the pyrometer. The optical constants of the LaAlO3 substrate and the YBa2Cu3O7−δ film are measured at high temperatures using a Fourier transform infrared spectrometer with a special sample holder that controls the sample temperature and oxygen pressure. The accuracy and precision of the ACP are demonstrated through both in situ and ex situ measurements. The present study facilitates exact and reproducible temperature control in high‐Tc superconducting film growth processes.  
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74.78.-w Superconducting films and low-dimensional structures
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.20.Ka High-temperature instrumentation; pyrometers

Particle contamination in low pressure organometallic chemical vapor deposition reactors: Methods of particle detection and causes of particle formation using a liquid alane (AlH3) precursor

Michael G. Simmonds, Wayne L. Gladfelter, Haojiang Li, and Peter H. McMurry

J. Vac. Sci. Technol. A 11, 3026 (1993); http://dx.doi.org/10.1116/1.578292 (8 pages) | Cited 2 times

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Two methods of analyzing particles were interfaced to a low pressure chemical vapor deposition reactor used to deposit Al films from the liquid precursor dimethylethylamine alane. A laser light scattering particle counter was used to monitor particles (≳200 nm) in real time and established that the appearance of particles corresponded to the flow of precursor into the reactor. A particle impaction system was used to collect particles (≳20 nm) for analysis using analytical transmission electron microscopy and electron diffraction. Typical sizes of the Al particles were in the range 20–1000 nm. Purposely introducing trace amounts of H2O, CO, and O2 into the reactor during the flow of the precursor caused an increase in the number of particles. Our results suggested that Al particle formation was induced by impurities in the gas phase (particularly H2O) although competing mechanisms could not be ruled out.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Conversion electron Mössbauer characterization of Fe–Ti and Fe–TiN interfaces in dependence on pretreatments and bias voltage in physical vapor depositiona)

Darko Hanžel, W. Meisel, D. Hanžel, P. Griesbach, B. Navinšek, P. Panjan, and P. Gütlich

J. Vac. Sci. Technol. A 11, 3034 (1993); http://dx.doi.org/10.1116/1.578293 (6 pages) | Cited 3 times

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Conversion electron Mössbauer (CEMS) and Auger electron spectroscopies (AES) were used to investigate the interfaces of Ti and TiN coatings on iron. The microstructure of the interface has been studied regarding the dependence on physical vapor deposition (PVD) parameters. In particular, the substrate temperature and the negative voltage (bias) applied during the PVD process were considered. An amorphous FexTi1−x phase has been identified at the interface of Fe/Ti. Its portion increases with increasing bias used during the deposition process. Mössbauer spectra also reveal a small amount of a magnetically ordered Fe–C phase in the FeTi interface. Its formation can be explained by a reaction of the residual gas in the PVD preparation chamber with iron. However, Fe/TiN interfaces show mainly iron carbide and/or nitride phases. Iron oxides always appear in the interfaces between the substrate and the deposited Ti or TiN thin films and their contribution increases when cleaning procedures in acetone and isopropyl alcohol were applied previous to the PVD deposition. They occur mostly in the form of magnetically ordered magnetite or/and in the form of small superparamagnetic particles, depending on the deposition conditions. Samples of Fe/Ti and Fe/TiN were annealed in vacuum at 773 K for 1 h, and CEMS spectra as well as AES depth profiles by argon ion sputtering were recorded. For the Fe/Ti interface, only minor changes were found. Fe/TiN interfaces, however, were found to be destabilized at an elevated temperature by an oxidative decomposition of TiN combined with reactions of the interface components with the substrate material.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.Nq Composition and phase identification
76.80.+y Mössbauer effect; other γ-ray spectroscopy

Kinetic model for the chemical vapor deposition of tungsten in the silane reduction process

Julian J. Hsieh

J. Vac. Sci. Technol. A 11, 3040 (1993); http://dx.doi.org/10.1116/1.578294 (7 pages) | Cited 4 times

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The kinetics involved in the chemical vapor disposition of tungsten, using the silane reduction chemistry, is modeled by a triple Eley–Rideal mechanism, which includes three competitive surface reaction pathways: (1) silane reduction of surface adsorbed WF6, (2) surface dissociation of silane and silicon reduction of WF6, and (3) (residual) hydrogen reduction of surface adsorbed WF6. The last two reaction pathways have not been properly considered in the past, and will be shown to be of critical importance to the understanding the complex Arrhenius behavior exhibited by the silane reduction process. A quantitative deposition rate expression, with no fitting parameters, is derived from the kinetic model using kinetic constants in the literature. The model can predict the deposition rate obtained experimentally, after taking into account the effect of reactant depletion in the reactor.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.Fd Collision theories; trajectory models

Vapor deposition of parylene‐F by pyrolysis of dibromotetrafluoro‐p‐xylene

L. You, G.‐R. Yang, C.‐I. Lang, J. A. Moore, P. Wu, J. F. McDonald, and T.‐M. Lu

J. Vac. Sci. Technol. A 11, 3047 (1993); http://dx.doi.org/10.1116/1.578295 (6 pages) | Cited 10 times

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Structural characteristics of poly(tetrafluoroparaxylylene) (PA‐F) films deposited directly from C6H4(CF2Br)2 precursor have been studied using Fourier transform infrared spectroscopy (FTIR) and x‐ray photoelectron spectroscopy (XPS). Zn was used as the catalyst and the vapor pyrolysis of precursor was carried out between 350 and 400 °C. It is shown that the FTIR and XPS spectra of the PA‐F films deposited from the precursor are comparable to those made from the conventional dimer route. Dissociation of the PA‐F films does not occur up to an annealing temperature of 500 °C. Both Zn and Br contaminants were observed in the XPS spectra. However, we found that the Br contamination disappears after annealing to an elevated temperature (≥350 °C), while Zn impurities still remain in the film.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films

Predicting intrawafer film thickness uniformity in an ultralow pressure chemical vapor deposition reactor

Gregory B. Raupp, Dimitris A. Levedakis, and Timothy S. Cale

J. Vac. Sci. Technol. A 11, 3053 (1993); http://dx.doi.org/10.1116/1.578296 (9 pages)

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We present a reaction engineering analysis of a multiple wafer‐in‐tube ultrahigh vacuum chemical vapor deposition reactor which allows an estimate of wafer throughput for a reactor of fixed geometry and a given deposition chemistry with specified film thickness uniformity constraints. The model employs a description of ballistic transport and reaction based on the pseudosteady approximation to the Boltzmann equation in the limit of pure molecular flow. The model representation takes the form of an integral equation for the flux of each reactant or intermediate species to the wafer surfaces. Expressions for the reactive sticking coefficients (RSC) for each species must be incorporated in the term which represents reemission from a wafer surface. In our model we use a published expression for the RSC of silane as a function of flux and wafer temperature developed from molecular beam measurements. Numerical solution of the resulting integral equation using Gauss–Legendre quadrature yields quantitative estimates of intrawafer film thickness uniformities for epitaxial silicon deposition from silane for specified process conditions and wafer radius:wafer separation. For given reactor dimensions and specified uniformity, throughputs can then be estimated.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Structural and optical studies in oxygenated amorphous CdTe films

F. J. Espinoza‐Beltran, O. Zelaya, F. Sanchez‐Sinencio, J. G. Mendoza‐Alvarez, M. H. Farias, and L. Baños

J. Vac. Sci. Technol. A 11, 3062 (1993); http://dx.doi.org/10.1116/1.578297 (5 pages) | Cited 8 times

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Amorphous oxygenated CdTe films (a‐CdTe:O) were grown by the radio‐frequency sputtering deposition technique in an Ar–N–O atmosphere; by increasing the nitrogen partial pressure in the growth chamber we are able to increase the amount of oxygen in the films in the range: 0–66 at. %. Auger analysis indicated that only Cd, Te, and O were present in the different samples. X‐ray diffraction patterns showed that the incorporation of oxygen leads to the amorphization of the zinc blende lattice. The optical absorption spectra for each sample was measured from optical transmission and photoacoustic techniques, and using the Tauc model for amorphous materials the band gap energy was obtained. From the analysis of the structural and optical measurements we propose that the a‐CdTe:O films are ternary semiconductors described by the formula: [CdTe]1−xOx, and that they do not show evidence of any phase mixture and/or precipitates.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Cd Deposition by sputtering

Stress stabilization of β‐tantalum and its crystal structure

Kazuaki Kondo, Masaaki Nakabayashi, Ken’ichi Kawakami, Tatsuo Chijimatsu, Masafumi Nakaishi, Masao Yamada, Masaki Yamabe, and Kenji Sugishima

J. Vac. Sci. Technol. A 11, 3067 (1993); http://dx.doi.org/10.1116/1.578298 (5 pages) | Cited 3 times

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We studied the relationship between Ta crystal structures and the stress stability of Ta under heating. The stress in Ta which was sputter deposited on SiC was unstable and changed more than 2×109 dyn/cm2 to the compressive side during heating at 200 °C for 30 min in air. In contrast, the stress in Ta which was sputter deposited on SiC whose surface was modified by Ar sputtering was very stable, and the stress change was less than 1.5×108 dyn/cm2 even after 6 h of heating at 200 °C. The x‐ray diffraction patterns of the Ta revealed that stable Ta was strongly (002) oriented β‐Ta, and that unstable Ta was randomly oriented β‐Ta with some α‐Ta. We found that amorphizing the SiC surface or inserting a thin amorphous interlayer enhanced growth of strongly (002) oriented β‐Ta.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.15.Cd Deposition by sputtering
85.40.Hp Lithography, masks and pattern transfer

Repair of a liquid metal ion emitter by a liquid metal ion emitter

F. G. Rüdenauer, H. M. Fehringer, W. Steiger, and A. Sieber

J. Vac. Sci. Technol. A 11, 3072 (1993); http://dx.doi.org/10.1116/1.578299 (4 pages)

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Liquid metal ion source (LMIS) indium emitters which have been poisoned by contamination with backsputtered material were successfully repaired by sputtering off the contamination layer, using a focused indium ion beam from an indium LMIS. It is essential that the repair beam consists of In ions to prevent the emitters from getting poisoned by the repair process itself. Poisoned emitters have excessively high firing voltages, but usually normal operating voltages. Following repair, firing voltage and operating voltage differed by not more than 150 V. Repairs worked equally well if the indium film on the emitter to be repaired was cold or hot (molten). Repairs were performed on fully assembled emitter modules where the emitter tip was recessed behind a stack of beam forming electrodes. Repair times are of the order of 10–15 min.
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29.25.Ni Ion sources: positive and negative

Interface studies between transition metals and poly(vilylidene fluoride)

F.‐M. Pan, J.‐L. Huang, and C.‐F. Liaw

J. Vac. Sci. Technol. A 11, 3076 (1993); http://dx.doi.org/10.1116/1.578300 (5 pages) | Cited 5 times

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The interfaces between poly(vilylidene fluoride) (PVDF) and the chromium film as well as the nickel film have been studied by x‐ray photoelectron spectroscopy (XPS). Chromium carbide and fluoride were formed at the interface when chromium was vapor deposited on the PVDF film. The chromium fluorides formed on the PVDF surface could be reduced by incoming Cr vapor atoms. According to mass spectroscopy, simple hydrocarbon gas species were produced during Cr deposition. While nickel carbide was detected by XPS on the Ni deposited PVDF, no fluoride was found on the substrate. In addition to simple hydrocarbon gas species, fluorocarbon gas product was produced during Ni deposition.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

New approach to quantitative surface photovoltage spectroscopy analysis

L. Kronik and Yoram Shapira

J. Vac. Sci. Technol. A 11, 3081 (1993); http://dx.doi.org/10.1116/1.578301 (4 pages) | Cited 5 times

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A new approach is presented for determining surface state parameters at semiconductor interfaces using time resolved surface photovoltage spectroscopy. The analysis provides precise determination of surface state energies, densities, occupancies, and cross sections for electrons and photons (including the wave‐length dependence of the photonic cross sections). Unlike previous methods, this approach does not require prior knowledge of the absolute band bending, but rather determines it among the other parameters. The algorithm is extended for any number of discrete surface energy levels.
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73.20.At Surface states, band structure, electron density of states

Evolution of atomic‐scale surface structures during ion bombardment: A fractal simulation

M. A. Shaheen and D. N. Ruzic

J. Vac. Sci. Technol. A 11, 3085 (1993); http://dx.doi.org/10.1116/1.578302 (7 pages) | Cited 7 times

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Surfaces of interest in microelectronics have been shown to exhibit fractal topographies on the atomic scale. A model utilizing self‐similar fractals to simulate surface roughness has been added to the ion bombardment code trim. The model has successfully predicted experimental sputtering yields of low energy (less then 1000 eV) Ar on Si and D on C using experimentally determined fractal dimensions. Under ion bombardment the fractal surface structures evolve as the atoms in the collision cascade are displaced or sputtered. These atoms have been tracked and the evolution of the surface in steps of one monolayer of flux has been determined. The Ar–Si system has been studied for incidence energies of 100 and 500 eV, and incidence angles of 0°, 30°, and 60°. As expected, normally incident ion bombardment tends to reduce the roughness of the surface, whereas large angle ion bombardment increases the degree of surface roughness. Of particular interest though, the surfaces are still locally self‐similar fractals after ion bombardment and a steady state fractal dimension is reached, except at large angles of incidence.
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61.80.Jh Ion radiation effects
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Magnetic force microscope combined with a scanning electron microscope

Atsushi Kikukawa, Sumio Hosaka, Yukio Honda, and Hajime Koyanagi

J. Vac. Sci. Technol. A 11, 3092 (1993); http://dx.doi.org/10.1116/1.578303 (7 pages) | Cited 8 times

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A magnetic force microscope (MFM) using frequency modulation detection was combined with a scanning electron microscope (SEM). The first goal was to facilitate the selection of the MFM imaging field by positioning the magnetic tip using the SEM. The second goal was to improve the performance of the MFM by operating it in a vacuum. The efficiency of the combined SEM was proved by imaging the particular region (about 3 μm in length) on the sample. The improved features of a MFM operated in a vacuum were demonstrated by comparing images taken in air and in a vacuum. The lateral resolution was improved to 50 nm in a vacuum while it was 100 nm in air, although that resolution could possibly be due to atomic force. The dependence of the MFM image on the tip to sample spacing is discussed also.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.55.-w Magnetic instruments and components

Modification of the x‐ray photoemission spectrum of in situ deposited thin films of Y1Ba2Cu3O7−y for various oxygen treatments

P. R. Broussard and V. C. Cestone

J. Vac. Sci. Technol. A 11, 3099 (1993); http://dx.doi.org/10.1116/1.578304 (7 pages) | Cited 2 times

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We have grown thin films of the Y1Ba2Cu3O7−y superconductor onto MgO and LaGaO3 substrates by off‐axis sputtering. The films were all deposited under the same conditions, but were cooled in various oxygen pressures resulting in films with superconducting transition temperatures from 85 K to nonsuperconducting. The samples have been examined by x‐ray photoemission spectroscopy without exposing the samples to air. We have characterized the core levels of Y, Ba, Cu, and O and the Auger parameter of Ba, Cu, and O as a function of the oxygen pressure used during cooldown. We find that the core lines sharpen and the Auger parameter for copper reduces as the oxygen pressure is decreased. We interpret this latter result as a possible change in the valence state of copper. We also see a variation in the valence structure.
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74.78.-w Superconducting films and low-dimensional structures
74.62.Fj Effects of pressure
74.25.Jb Electronic structure (photoemission, etc.)
79.60.Dp Adsorbed layers and thin films

Temperature‐dependent x‐ray photoelectron diffraction of Pb(100): Experimental results and the single‐scattering cluster model

E. A. Murphy, H. E. Elsayed‐Ali, Ken T. Park, and Y. Gao

J. Vac. Sci. Technol. A 11, 3106 (1993); http://dx.doi.org/10.1116/1.578305 (5 pages) | Cited 1 time

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An angle‐resolved x‐ray photoelectron diffraction study of the temperature‐dependent surface structure of Pb(100) is performed. Below 550±11 K, the decrease in forward‐scattered intensity attenuation is exponential with temperature. The intensity attenuation of the forward‐scattered peaks is much larger than predicted by both single‐scattering and multiple‐scattering x‐ray photoelectron diffraction models for a bulklike lattice. Corrections for surface relaxation and thermal expansion in the single‐scattering cluster model result in an increase in the predicted intensity attenuation; however, sufficient agreement between experiment and calculation is not achieved.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ja Surface and interface dynamics and vibrations
61.05.J- Electron diffraction and scattering

Measurement of CO pressures in the ultrahigh vacuum regime using resonance‐enhanced multiphoton‐ionization time‐of‐flight mass spectroscopy

J. Patrick Looney, Joel E. Harrington, Kermit C. Smyth, Thomas R. O’Brian, and Thomas B. Lucatorto

J. Vac. Sci. Technol. A 11, 3111 (1993); http://dx.doi.org/10.1116/1.578306 (10 pages) | Cited 8 times

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An evaluation is made of measurements of CO pressures in the UHV regime using resonance‐enhanced multiphoton ionization coupled with time‐of‐flight mass spectroscopy (REMPI‐TOFMS). It has been found that once the REMPI‐TOFMS system has been calibrated, quantitative measurement of CO pressures as low as 10−10 Pa is possible, even in overwhelming N2 backgrounds. With compensation for laser pulse energy variations, we find measurements with uncertainties of 10%–15% are possible for pressures down to 10−7 Pa, and an ultimate detection limit for CO pressures of 10−10 Pa for our measurement system. In this study, the REMPI‐TOFMS system was calibrated using a pressure division technique along with a spinning rotor gage. The ionization of CO is achieved using 230 nm radiation to excite the B 1Σ+ state of CO at 10.8 eV via a two‐photon absorption and then ionizing some of the excited state molecules by the absorption of an additional photon from the laser beam.
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07.30.Dz Vacuum gauges

Hybrid Cu–Al beam pipe for KEK B factory

Hajime Ishimaru, Takashi Momose, Yusuke Suetsugu, and Hideo Hirayama

J. Vac. Sci. Technol. A 11, 3121 (1993); http://dx.doi.org/10.1116/1.578307 (5 pages)

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A hybrid Cu–Al beam pipe is proposed for the KEK B factory. The pipe design is based on the idea that the best characteristics of each material should be utilized to obtain lower cost and a photodesorption yield comparable to that of an all‐copper vacuum beam pipe. Copper is used in the part directly irradiated by synchrotron radiation photons while aluminum alloy is used in the parts irradiated only by reflected photons. A fabricated model of the hybrid Cu–Al beam pipe is presented, and can be realized using standard manufacturing techniques. For the present, the desorption yield of aluminum alloy is estimated as about five times higher than that of copper. Using this value, the estimated photodesorption yield is about three times higher than that of an all‐copper beam pipe, at a photon dose greater than 1021 photons/m. The photodesorption yield of the aluminum alloy must be reduced, and several methods are suggested to obtain a yield comparable to copper. Using EGS4, the estimated radiation levels outside of the hybrid beam pipe in the normal bending sections of both the high energy ring and the low energy ring for the KEK B factory are comparable with those in the existing TRISTAN accumulation ring. In the wiggler sections, however, an additional order of magnitude in shielding is required to reach the same levels. The present estimated cost of the hybrid beam pipe is one third that of an all‐copper beam pipe and is 0.6 million yen per meter.
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29.20.dk Synchrotrons
29.27.Eg Beam handling; beam transport

Perspectives and limitations of vacuum microtubes

S. Mil’shtein, C. A. Paludi, P. Chau, and J. Awrach

J. Vac. Sci. Technol. A 11, 3126 (1993); http://dx.doi.org/10.1116/1.578460 (4 pages) | Cited 1 time

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The edge or blade type emitter is the basic element of design for vacuum microtubes presented in this article. Several devices are tested which consist of vertical and horizontal structures with two (diode), three (triode), and four (tetrode) electrodes. The experimental results show some correlation with Fowler–Nordheim (FN) theory. In cases where emission occurs, but FN theory is not followed, the results indicate limitations in the ability to model, and to account for those factors which control emission. The cold emission from the grid (gate) electrode, and the phenomena of ‘‘forming’’ a metal surface are also discussed. The difficulty in controlling cold emission makes these devices inflexible. One can conclude from analyzing the experimental results presented in this paper, as well as similar results obtained from other research, that cold emission devices have a number of drawbacks and limitations regardless of the design of the emitter. To mitigate these drawbacks and limitations, a new design for a vacuum microtube is presented which operates on the basis of photoemission, and offers an alternate control mechanism for more stable emission.
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84.47.+w Vacuum tubes

Film deposition with a facing magnets magnetron sputtering method

Qihua Fan, Xiaohong Chen, Hongyou Chen, and Yuan Hong

J. Vac. Sci. Technol. A 11, 3130 (1993); http://dx.doi.org/10.1116/1.578461 (3 pages) | Cited 1 time

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A new type of cathode sputtering apparatus with two annular magnets facing each other has been developed. It cannot only deposit films at high rate and low substrate temperature but also greatly improve the target utilization and film thickness uniformity. The maximum deposition rate of Cu films was about 12 000 Å/min. The substrate temperature was not elevated above 55 °C during sputtering. Target utilization rate was improved to about 54%. For a target of 80 mm in diameter, the uniformity of Cu film thickness was better than ±5% over a region of about 56 mm in diameter.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

Calibration of type‐C thermocouples to liquid helium temperature

William J. Mitchell, Jun Xie, and W. Henry Weinberg

J. Vac. Sci. Technol. A 11, 3133 (1993); http://dx.doi.org/10.1116/1.578462 (2 pages)

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Abstract Unavailable
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07.20.Dt Thermometers
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

A permanent, retractable screen for charge neutralization of insulating specimens during x‐ray photoelectron spectroscopy analysis

G. D. Davis, C. R. Anderson, and H. M. Clearfield

J. Vac. Sci. Technol. A 11, 3135 (1993); http://dx.doi.org/10.1116/1.578463 (3 pages)

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Differential charging that occurs during x‐ray photoelectron spectroscopy analysis of insulating specimens is especially problematic in systems incorporating a focused, monochromatic x‐ray source. Often, a grounded charge compensation screen is used in conjunction with an electron flood gun to alleviate this problem. Because the use of such a screen can be inconvenient or impossible in some experiments, we have developed a method by which it can be permanently incorporated into the analysis chamber and retracted when not in use. We describe two such applications. In one, we also incorporate a phosphor screen and analysis standards. The use of a retractable screen allows cyclic surface modification/film deposition/characterization studies to be achieved conveniently on insulating specimens.
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07.85.-m X- and γ-ray instruments
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Inexpensive spot‐profile analysis reflection high energy electron diffraction

Yves Idzerda

J. Vac. Sci. Technol. A 11, 3138 (1993); http://dx.doi.org/10.1116/1.578464 (3 pages) | Cited 1 time

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A simple, photomultiplier based spot‐profile analysis reflection high energy electron diffraction (SPARHEED) apparatus is described. A micrometer scanned, two pinhole aperture is coupled to an optical fiber and yields 38 μm spot‐profile intensity resolution of RHEED patterns corresponding to an ultimate spatial resolution of ∼4000 Å along the RHEED pattern and 900 Å across the RHEED pattern. Long range scanning also allows for surface lattice net determination. Acquisition of selected RHEED intensity oscillations is straightforward. The device is easily mounted, rigid, and inexpensive.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Movable mask for Riber Si molecular beam epitaxy system

T. C. Zhou

J. Vac. Sci. Technol. A 11, 3141 (1993); http://dx.doi.org/10.1116/1.578465 (2 pages)

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Abstract Unavailable
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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
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