bluuebunny/crossref_metadata_2025 huggingface dataset:
Electric states of segregated metal atom on metal surfaces and potential use for field emitter
Authors: Yoshitake Michiko , Yoshihara Kazuhiro
Published: July 2002

Segregation phenomenon of substrate copper atoms onto rf sputter-deposited titanium film was observed using Auger electron spectroscopy and x-ray photoelectron spectroscopy. When the specimens were heated, Cu atom diffused onto the surface of Ti film from the substrate with the diffusion constant bigger than that of the bulk diffusion by three orders of magnitude. The surface concentration of Cu saturated at about 5%. If the segregated layer was removed by sputtering, the saturated Cu concentration on the surface was easily reformed by heating. The saturation concentration was constant at heating temperatures between 710 and 850 K. This was interpreted to mean that the saturated surface composition is thermodynamically achieved and is easy to reproduce. The binding energy of Cu 2p3/2 of the segregated Cu was 0.24 eV higher than that of the pure metal. The amount of the charge transfer from Cu to Ti was assumed to vary linearly with the chemical shift, and the decrease in the work function due to the segregation layer of Cu was estimated to be 0.62 eV. Therefore, surface segregation is postulated to be a method to reproducibly decrease the work function and is potentially useful to manufacture materials for a field emitter.
Influence of angular distribution on the deposition rate of species sputtered from a multicomponent target in different configurations: Applications to mixed valence copper oxides
Authors: Lecoeur Philippe , Mercey Bernard , Murray Hugues
Published: July 2002

This work deals with calculation of the thickness distribution of films deposited by sputtering in different configurations: ‘‘on axis’’ and ‘‘off axis’’ diodes, facing target and hollow cathode, and for different polar distributions of ejected species. We demonstrate that a difference in the polar distribution may induce deviations from stoichiometry especially in the diode configuration. In the facing target and hollow cathode configurations, the deviations are strongly reduced. The theoretical calculations fit well with the experimental results that were obtained with mixed valence copper oxide sputtered films.
Disorder effects at the Al(110) surface
Authors: Schommers W. , Mayer C. , Göbel H. , von Blanckenhagen P.
Published: July 2002

In this article we report on molecular dynamics calculations of Al(110) surfaces using a temperature-dependent pair potential. The main qualitative trends and results agree well with experimental data.
Plasma source ion nitriding: A new low temperature, low-pressure nitriding approach
Authors: Lei M. K. , Zhang Z. L.
Published: July 2002

Plasma source ion nitriding is a new approach for surface modification of steel with certain advantages over conventional plasma nitriding and plasma-based nitrogen ion implantation. A nitriding apparatus based on an electron cyclotron resonance (ECR) microwave plasma source has been developed. Nitrogen ions are accelerated from the ECR microwave plasma by a low-pulsed negative bias (typically −2 kV) which is applied directly to the workpiece, implanted, and finally diffused into the steel at elevated temperatures that are regulated up to 550 °C by an auxiliary heater. An application of plasma source ion nitriding into 1Cr18Ni9Ti austenitic stainless steel is described. The nitriding layer thicknesses are varied continuously from 0.8 to 10 μm at various process temperatures from 230 to 480 °C for a nitriding time of 4 h. A dramatic increase in microhardness has been observed. Glancing angle x-ray diffraction has been used to determine the structural changes that occur in the nitrided surface layer.
Effect of the composition and anion vacancies in the band gap and band levels of Cu–In–Se–Te thin films
Authors: Díaz R. , León M.
Published: July 2002

Cu–In–Se–Te thin films grown by ‘‘flash’’ evaporation present stoichiometric deviations with anion vacancies and Cu excess. These changes in composition produce a different band structure. The effect of composition variations and anion vacancies in the energy gap is analyzed and a schematic band level is drawn. Samples with lower numbers of anions present conduction band minima (CBM) and valence band maxima (VBM) lower than samples with higher numbers of anions. The variation in VBM is greater than in CBM.
Imaging an F-actin structure with noncontact scanning force microscopy
Authors: Braunstein David
Published: July 2002

F-actin, a ubiquitous cytoskeletal protein, crucial to cell function and motility, was used as a test sample to compare the resolution limits of non-contact scanning force microscopy (NCSFM) to that standard of contact scanning force microscopy (SFM). NCSFM probes the surface topography of a sample without direct physical contact between the atomic force microscope cantilever tip and the sample surface, avoiding the type of tip sample damage that one encounters with standard contact SFM. NCSFM images of rhodamine–phalloidin stabilized F-actin deposited on polished sapphire substrates clearly show filamentous structures on the substrate surface with ∼36 nm periodicity. The polished sapphire substrates present a positive surface charge at pH 7 that complements the negative surface charge of F-actin during deposition and provides a clean, hard surface. Contact SFM images of the same samples, although showing filaments on the substrate surface, display a lower overall clarity compared to the NCSFM images.
Top ten list of user-hostile interface design: The ten most frequent mistakes made in human–computer interface design
Authors: Miller Dwight P.
Published: July 2002

This article describes ten of the most frequent ergonomic problems found in human–computer interfaces (HCIs) associated with complex industrial machines. In contrast with being thought of a ‘‘user friendly,’’ many of these machines are seen as exhibiting ‘‘user-hostile’’ attributes by the author. The historical lack of consistent application of ergonomic principles in the HCIs has led to a breed of very sophisticated, complex manufacturing systems that few people can operate without extensive orientation, training, or experience. This design oversight has produced the need for customized training programs and help documentation, unnecessary machine downtime, and reduced productivity resulting from operator stress and confusion. The ten issues are treated in a problem–solution format with real-world graphic examples of good and poor design. Intended for a diverse audience, the article avoids technical jargon, and is appropriate reading for those involved in software, product engineering, marketing, and management.
Secondary ion mass spectroscopy analysis for aluminum surfaces treated by glow discharge cleaning
Authors: Chen J. R. , Hsiung G. Y. , Liu Y. C. , Lee W. H. , Nee C. C.
Published: July 2002

Glow discharge cleaning treatments on aluminum surfaces were studied by the secondary ion mass spectroscopy method. The cleaning effects of direct current and radio frequency glow discharges with H2 and Ar gases were compared. The elements or compounds of the contamination or reaction depositions were identified from analyses of the mass spectra and energy distribution of the secondary ions. Base material, chemical solvents, sputtered depositions, hydrogen –oxygen–hydroxyls, and hydrocarbons were the five major sources of the secondary ions. The energy distribution curves were similar for secondary ions with similar compound complexity, and the cleaning effects were nearly identical for secondary ions with the same type of origin.
Epitaxial growth of a metal(CoSi2)/insulator(CaF2) nanometer-thick heterostructure and its application to quantum-effect devices
Authors: Asada M. , Watanabe M. , Suemasu T. , Kohno Y. , Saitoh W.
Published: July 2002

Metal(CoSi2)/insulator(CaF2) nanometer-thick heterostructures are grown on a Si(111) substrate, and applied to quantum-effect electron devices. In the epitaxial growth of a CoSi2/CaF2 multilayer, an epitaxial CoSi2 layer on CaF2 was obtained by the two-step growth technique, i.e., solid phase epitaxy with the epitaxial Si layer grown in the first step and Co deposited in the second step. An epitaxial CaF2 layer was formed on CoSi2/CaF2 at the low substrate temperature of 450 °C with a partially ionized and accelerated CaF2 beam. Co agglomeration in nanometer-thick CoSi2 layer was avoided by using these techniques. A resonant tunneling transistor with double CoSi2 quantum wells was fabricated, and a transistor action with the negative differential resistance was observed at 77 K. The transfer efficiency of electrons from the emitter to the collector through the resonant energy levels is estimated to be close to unity. A resonant hot electron transistor structure was also fabricated, and multiple negative differential resistance was observed, which may be attributed to the interference of electrons through the insulator conduction band in the metal–insulator–metal structure.
High-aspect-ratio Si etching for microsensor fabrication
Authors: Juan W. H. , Pang S. W.
Published: July 2002

Etching of high-aspect-ratio Si structures for microsensors was carried out in a Cl2 plasma generated by a multipolar electron cyclotron resonance (ECR) source. Si etch rate is found to increase with microwave and rf power, and it is the highest at 1 mTorr over the range of 0.5–50 mTorr. Optical emission spectroscopy (OES) and mass spectrometry (MS) were used to monitor the etch process to provide precise control for the sensor fabrication. The Si emission intensity at 288.1 nm and the mass spectrometric signal for 63SiCl+ follow the Si etch rate directly. The selectivity of etch masks decreases at higher rf power and Ni has higher selectivity than SiO2. Si etch rate is reduced for structures with smaller linewidth, but this microloading effect decreases at lower pressure. For the etch conditions used, the Si etch rate remains almost constant when flow rate is changed, but the optical emission and mass spectrometric signals of the etch products are found to decrease with increasing flow. Endpoint detection is applied to monitor etching of the resonators. Both OES and MS provide a clear indication when the polycrystalline Si is etched down to the oxide layer. With a Cl2 plasma at 3 mTorr, 100 W microwave power, 100 W rf power, and 8 cm below the ECR source, high-aspect-ratio microstructures in Si with vertical profile and smooth morphology were etched. These sensing elements are 28 μm deep with 1.5 μm gap, providing a high aspect ratio of 19 in Si. The width of the elements was reduced by oxidation followed by wet etching of the dry etched microstructures to provide better sensitivity for the microsensors.
A molecular dynamics study of transient processes during deposition on (001) metal surfaces
Authors: Gilmore C. M. , Sprague J. A.
Published: July 2002

Strong reflection high-energy electron diffraction oscillations have been observed during growth of Cu onto (001)Ag substrates at 77 K [W. F. Egelhoff and I. Jacob, Phys. Rev. Lett. 62, 921 (1989)]. This result indicates layer by layer film growth and surface mobility of the deposited atoms. This unexpected result was explained by proposing a ‘‘transient mobility’’ to account for layer growth. We have utilized molecular dynamics simulations with the embedded atom method to study transient processes that occur over hundreds of picoseconds. Transient processes were observed that promoted the formation of clusters, and other processes were observed that resulted in spreading atoms across the surface.
Depth profiling free carbon in silicon carbide
Authors: Paulson T. E. , Bojan V. J. , Wichterman B. M. , Pantano C. G.
Published: July 2002

A fingerprint for free carbon was identified from the negative ion mass spectra of various carbon and silicon carbide standards. It was found that high-mass carbon molecular species can be used to distinguish free carbon in silicon carbide. Secondary ion mass spectrometry (SIMS) depth profiling (12 keV Cs+ primary beam, negative SIMS mode) was used to calculate the useful yield of negatively charged molecular carbon ions from carbon (in various forms) and silicon carbide. The useful yield ratio of C−n molecules from carbon to SiC increased with increasing n, meaning higher mass molecular carbon species are more likely to originate from free carbon than silicon carbide. 72C−6 and 96C−8 species were used to depth profile free carbon in chemically vapor deposited SiC/C coatings on SCS-0 and SCS-6 silicon carbide fibers.
Ion incident angle dependence of material properties of a ZrN film on silicon prepared by the ion assisted deposition method
Authors: Horita Susumu , Akahori Hiroshi , Kobayashi Mituru
Published: July 2002

The crystalline quality, resistivity, chemical composition, and surface morphology of a ZrN film deposited on a Si(100) substrate by an ion assisted deposition method were investigated as functions of the incident angle of an ion beam. By this method, metallic Zr is deposited by electron-beam evaporation while simultaneously bombarding the film with nitrogen ions having an energy of 400–600 eV. The incident angle was changed from 15° to 90° between the ion beam and the plane of the substrate. It was found that the crystalline quality of the ZrN film improved by decreasing the incident angle from 90° to 48°. This is partly because, by lowering the incident angle, the normal momentum component of the ion beam to the growing film is decreased so that the radiation damage due to ion bombardment is reduced and partly because the horizontal component is increased to enhance the migration of the adatoms on the surface of the film. Also, it was found that the resistivity decreased by lowering the incident angle. However, at incident angles ≤30°, the surface of the growing film was roughened at the initial deposition stage and eventually the film peeled off the substrate because of the formation of zirconium silicide at the interface between the ZrN film and the Si substrate. On the other hand, the chemical composition of the ZrN film was found to be almost stoichiometric for any incident angle. It was concluded that the optimum incident angle of an ion beam is around 45° for the highest crystalline quality, lowest resistivity, and smoothest surface morphology.
Beam vacuum system of Brookhaven’s muon storage ring
Authors: Hseuh H. C. , Snydstrup L. , Mapes M. , Pai C.
Published: July 2002

A storage ring with a circumference of 45 m is being built at Brookhaven to measure the g-2 value of the muons to an accuracy of 0.35 ppm. The beam vacuum system of the storage ring will operate at 10−7 Torr and has to be completely nonmagnetic. It consists of 12 sector chambers. The chambers are constructed of aluminum alloy and are approximately 3.5 m in length with a rectangular cross section 16.5 cm high by 45 cm at the widest point. The design features, fabrication techniques, and cleaning methods for these chambers are described. The beam vacuum system will be pumped by 48 nonmagnetic distributed ion pumps with a total pumping speed of over 2000 ℓ/s. Monte Carlo simulations of the pressure distribution in the muon storage region are presented.
Starting delays in cold-cathode gauges at low pressures
Authors: Kendall B. R. F. , Drubetsky E.
Published: July 2002

A cold-cathode gauge does not immediately start when power is applied. Starting is generally assumed to be triggered by a cosmic ray or other energetic particle. The starting behaviors of two magnetron, two inverted magnetron, and five double inverted magnetron gauges were studied at pressures ranging from 2×10−7 down to 10−10 Torr. The effects of various starting devices (beta, alpha, field-electron, and photon emitters) were also evaluated. The median starting time for a given gauge was found to be approximately inversely proportional to pressure and consisted of two distinct components: a dormant interval and a growth period. The dormant interval is inherently nonreproducible, being governed by the statistical laws of random events. It can only be quantified by taking the median of a large number of measurements. It is normally by far the larger component and can amount to hours or days at 10−10 Torr. The growth period, on the other hand, is highly reproducible. It typically has a value of about 1 min at 10−10 Torr. For most of the growth period the discharge current is below the limit of detection, making it necessary to use special experimental techniques to determine the true growth period. A double inverted magnetron with radioactive triggering to reduce the dormant interval to less than a second at 10−10 Torr is described. Sources of error in starting-time measurements are discussed.
Physical properties of diamondlike carbon films deposited in mixed atmospheres of C2H4–Ar, C2H4–H2, and C2H4–N2
Authors: Nakayama Masatoshi , Matsuba Yasuhiro , Shimamura Junichi , Yamamoto Yasuyuki , Chihara Hiroshi , Kato Hideo , Maruyama Kazunori , Kamata Kiichiro
Published: July 2002

Diamondlike carbon films were deposited in a pure C2H4 atmosphere and in mixed atmospheres of C2H4–Ar, C2H4–H2, and C2H4–N2 by radio frequency plasma chemical vapor deposition. The partial pressures of Ar, H2, and N2 were 25%, 50%, and 66.7%, respectively. The films were deposited with a high negative bias of −610 V. The hardness, the density, and the internal stress of the films decrease and the amount of gas evolution increases with increasing partial pressures of N2 and H2, while they do not depend on the partial pressure of Ar. These results show that N2 and H2 react with carbon in the films and decrease the degree of the crosslinking in the network structure, while Ar does not change the degree of crosslinking. The surface is very flat and the roughness (Rmax) is below 1 nm. The hardness is 40 GPa for the films deposited in atmospheres of pure C2H4 and mixed C2H4–Ar with a bias of −610 V.
Plasma crystal
Authors: Morfill G. E. , Thomas H.
Published: July 2002

Plasma crystal is the term used to describe the recently discovered ordered state that a colloidal plasma may assume under certain conditions. This state resembles metals, to some extent, with the ‘‘atoms’’ represented by the highly negatively charged and highly ordered colloidal particles and the ‘‘electrons’’ by the mobile plasma ions and electrons—perhaps ‘‘heavy metal’’ might be an appropriate description. Plasma crystals are formed in a colloidal plasma if two conditions are met: (1) The Coulomb coupling parameter (the ratio of the Coulomb energy between neighboring particles to their kinetic energy) exceeds a certain threshold and (2) the lattice parameter (the ratio of the particle separation to the Debye length) is smaller than unity. These conditions are easy to generate in rf discharge plasmas and plasma crystallization then proceeds spontaneously. Plasma crystals have some unique properties, which make them exciting systems to study. (1) In their own right, as a hitherto unknown form of condensed plasma, they may provide many insights into basic plasma physical processes and transport effects. (2) As model systems for the detailed investigation of phase transitions, lattice defects, annealing, doping, etc., they may provide new information for a better understanding of solid state physics. (3) As test systems they may be useful for investigating nonlinear effects in ‘‘nanocrystals’’ (crystals with less than approximately 100 lattice planes).

The unique properties, which enable these investigations and possibly many more, are (1) global charge neutrality, (2) very fast response, (3) very little damping, and (4) easy experimental control and diagnostics, i.e., detailed imaging and high temporal resolution of the dynamics of individual particles (‘‘atoms’’). We present here an overview of recent developments in this new research field.
Effect of gas composition and bias voltage on the structure and properties of a-C:H/SiO2 nanocomposite thin films prepared by plasma-enhanced chemical-vapor deposition
Authors: Lee Jung H. , Lee Young H. , Farouk Bakhtier
Published: July 2002

The effects of gas flow rate ratio and bias voltage on the structure and properties of a-C:H and SiO2 nanocomposite thin film are investigated. The film depositions are performed in a 13.56 MHz, rf driven asymmetric plasma reactor using a mixture of styrene as the source gas for a-C:H, tetraethylorthosilicate (TEOS) as the source gas for SiO2, and hydrogen as a diluent. The structure and properties of the films are evaluated by ellipsometry, Fourier transform infrared (FTIR), Rutherford backscattering spectrometry stress gauge, and ultraviolet-visible spectrometer. The growth rate of the film appears to follow Langmuir–Hinshelwood kinetics. The film structure evaluated by FTIR shows that the nanocomposite film has characteristic peaks of a-C:H and SiO2 components. From the overlapped bands of Si–O and C–O stretching modes, it is deduced that SiO—C bonds are formed in the film via ion-assisted reactions. As the fraction of TEOS flow rate is increased, the refractive index, intrinsic stress, and graphitization of the film decrease, while the transparency of the film in the visible region increases. As the negative bias voltage at the substrate is increased during the film deposition, the refractive index, intrinsic stress, and graphitization increase, while the growth rate and the hydrogen content of the film decrease.
Growth behavior of copper metalorganic chemical vapor deposition using the (hfac)Cu(VTMOS) precursor on titanium nitride substrates
Authors: Jun Chi-Hoon , Kim Youn Tae , Baek Jong-Tae , Yoo Hyung Joun , Kim Dai-Ryong
Published: July 2002

Metalorganic chemical vapor deposition of copper using the thermally stable (hfac)Cu(VTMOS) [C10H13O5CuF6Si: 1,1,1,5,5,5-hexafluoro-2,4 pentadionato(vinyltrimethoxysilane) copper (I)] precursor has been carried out on TiN substrates prepared by physical vapor deposition (PVD) and rapid thermal processing (RTP). The apparent activation energies over substrate temperatures ranging from 160 to 220 °C were about 7.5 kcal/mol on the PVD-TiN and 9.7 kcal/mol on the RTP-TiN. The higher growth rate of the copper deposit on the RTP-TiN could be ascribed to the increase in nucleation sites and the higher electron catalytic reactivity, resulting in enhancement of copper nucleation density in the initial stages of film growth. The copper deposits revealed polycrystalline phases with a preferred orientation of (111), and impurities within the films were below the detection limit of Auger electron spectroscopy. As substrate temperature increased, the copper films on the PVD-TiN developed as a columnar structure according to the Volmer–Weber growth mode, and on the RTP-TiN a nearly equiaxed structure was formed presumably by Stranski–Krastanov grain growth. The electrical resistivity of the deposits on the PVD-TiN and the RTP-TiN was in the range 2.8–5.4 μΩ cm for 1500–3100 Å film thicknesses and 4.4–6.2 μΩ cm for 2300–4300 Å film thicknesses, respectively. With increasing film thickness, the electrical resistivity of the copper layers linearly increased on the PVD-TiN, while it gradually decreased on the RTP-TiN. Consequently, the variations in the electrical resistivity of the deposits could be explained by changes in microstructures of the copper films, due to different growth behavior of copper on the two types of substrates.
Near-edge x-ray absorption fine structure characterization of compositions and reactivities of transition metal oxides
Authors: Chen J. G. , Frühberger B. , Colaianni M. L.
Published: July 2002

We have applied the near-edge x-ray absorption fine structure (NEXAFS) technique to characterize the systematic trends in the oxygen K edge and metal L edge features of powder materials of 3d transition metal oxides. In agreement with previous high energy electron energy loss spectroscopy data [L. A. Grunes et al., Phys. Rev. B 25, 7157 (1982)], our NEXAFS results demonstrate that the characteristic oxygen K-edge features are related to the number of d electrons in the transition metal oxides. By comparison with these model compounds data, we have applied NEXAFS to investigate the compositions and reactivities of thin oxide overlayers on several single crystal surfaces, including V(110), Mo(110), and Ni(100). We will use several examples to demonstrate the capabilities of NEXAFS, such as the determination of surface O/M stoichiometries, the differentiation between atomic and molecular oxygen species on surfaces, and the determination of reaction kinetics under in situ conditions. Finally, direct differentiation of surface and bulk compositions of metal oxides will also be discussed by comparing the NEXAFS data collected by means of the surface-sensitive electron-yield and bulk-sensitive fluorescence-yield methods.
Electroluminescent displays
Authors: King Christopher N.
Published: July 2002

This article will review the electrical and optical properties of thin film electroluminescent (EL) displays. A simple electrical model for thin film electroluminescent (TFEL) device operation will be presented and used to describe the luminance and power consumption of TFEL devices. The basic material characteristics that are desirable for EL phosphors will be described. Progress in the development of multicolor and full color EL displays will be presented including device structures and phosphor advancements. Recent work on devices that combine EL technology with high resolution active matrix circuitry to achieve high resolution displays for head-mounted applications will be described.
Scaleup of a nitrogen glow-discharge process for silver–poly(ethylene terephthalate) adhesion
Authors: Grace J. M. , Freeman D. R. , Corts R. , Kosel W.
Published: July 2002

In situ studies of plasma-treated poly(ethylene terephthalate) [PET] followed by metallization suggested a viable process for treating and silver coating PET support to manufacture suitable silver-coated base material. Following this work and some proof-of-principle demonstrations on a pilot scale, a successful process was delivered at the manufacturing scale. The scaleup process consisted of running a multifactor experiment on a pilot machine, installing the necessary production equipment on a production coater, and carrying out a smaller multifactor experiment on the production machine to aid in selection of manufacturing conditions. Key to the success of this scaleup process was the ability to measure silver–PET adhesion in a sufficiently quantitative and practical manner. For this purpose a salt bath adhesion test was developed. By using this test as an experimental response, robust operating conditions were found. Furthermore, the test provided a means to troubleshoot, track the process, and establish performance/cost trade-offs. The adhesion test and the pilot and production experiments are discussed.
Study of particulate formation and its control by a radio frequency power modulation in the reactive ion etching process of SiO2 with CF4/H2 plasma
Authors: Yeon Chung-Kyu , Whang Ki-Woong
Published: July 2002

Particulate formation in the reactive ion etching process of SiO2 with a CF4/H2 plasma was studied with the laser light scattering (LLS) method. The LLS onset time decreases drastically as the hydrogen percentage increases which indicates that the particulate formation was stimulated by the increase of the unsaturated fluorocarbon species as a result of the hydrogen addition. The onset time was also dependent on the substrate material. The measured onset time with a Si wafer was shorter than that with a SiO2 wafer. The onset time decreases very rapidly with the increase of the radio frequency (rf) power. A decrease of the LLS peak intensity was observed with the square wave modulation process of rf power. The change of the etch rate and the LLS peak intensity according to the change of the duty ratio shows that the optimal process condition, which satisfies high selectivity, high etch rate, and low particulate growth level, can be obtained with the rf modulation method. In the rf modulation process, both an increase in the off period and a decrease in the on period resulted in a decrease of the LLS signal in the particulate trap. It was observed that a change in the off period has a more pronounced effect on the change of the LLS signal intensity.
Pulse-modulated infrared-laser interferometric thermometry for non-contact silicon substrate temperature measurement
Authors: Kikuchi Jun , Fujimura Shuzo , Kurosaki Ryo , Yano Hiroshi
Published: July 2002

We present a simple interferometric thermometry for non-contact temperature measurement of silicon substrates. When pulse-modulated light from an InGaAsP infrared laser diode was directed at a silicon wafer polished on both sides, overshoot and undershoot behaviors in the transmitted light intensity were observed. These phenomena were utilized to determine the direction of temperature change. We measured the temperature of a silicon wafer under successive heating and cooling. This temperature monitor was able to measure up to 600 °C with 1.3 μm wavelength laser and 700 °C with a 1.55 μm one. By shortening the cycle time of the pulse modulation, this method can follow temperature changes as fast as 450 °C/s for 0.5-mm-thick silicon wafers.
Comparison of surface oxidation of titanium nitride and chromium nitride films studied by x-ray absorption and photoelectron spectroscopy
Authors: Esaka F. , Furuya K. , Shimada H. , Imamura M. , Matsubayashi N. , Sato H. , Nishijima A. , Kawana A. , Ichimura H. , Kikuchi T.
Published: July 2002

Surface oxidation mechanisms of TiN and CrN films were studied by means of x-ray photoelectron (XPS) and absorption spectroscopy (XAS). In the N 1s XPS spectra of both the oxidized TiN and CrN films, a feature assigned to molecular nitrogen was observed in addition to a feature assigned to nitride. The assignment was confirmed by the N K-edge XAS spectra of the TiN and CrN films which exhibited a sharp feature at 401.4 eV. Besides these features, the N 1s XPS spectra of the oxidized TiN films showed a third feature, which was assigned to NX–Ti–OY like structures taking into account the change in the Ti 2p XPS spectra. However, no evident feature assigned to NX–Ti–OY like structures was observed in the XAS spectra because of the overlapping with the nitride features. The above results indicated that the CrN films directly changed to Cr2O3 with the formation of molecular nitrogen in the interstitial positions of the surface oxide layers, while the TiN films were oxidized to TiO2 through the formation of NX–Ti–OY like structures. The formation of the NX–Ti–OY like structures may allow the rapid diffusion of oxygen and hence lower the oxidation resistance of TiN films.
Mass and energy measurements of the species responsible for cBN growth in rf bias sputter conditions
Authors: Tsuda Osamu , Tatebayashi Yoshinao , Yamada-Takamura Yukiko , Yoshida Toyonobu
Published: July 2002

Mass and energy measurements of ions and neutrals impinging on a substrate surface were performed during radio frequency (rf) bias sputter deposition of cubic boron nitride (cBN) thin films in a pure Ar discharge. The sampling system was rf driven to measure the correct energy of ions impinging to the rf driven substrate. The ion energy distributions showed asymmetric bimodal shapes and the energy spreads varied with the masses of ions and the negative substrate bias voltage (Vs). Ar+ was the most dominant ion, and the average energy and energy spread changed with Vs from 90 to 310 eV and from 40 to 140 eV, respectively. The flux ratio of Ar+ to B (Φi/ΦB) increased from 1.0 to 2.3 with a decrease in the target power input. cBN could be deposited above a threshold of the total momentum transfer per depositing boron atoms; 138 (eV amu)1/2, which is comparable to the values reported in the ion beam assisted depositions. Therefore, argon ions with an energy of 135 to 380 eV are considered to be equally contributory for cBN formation. Moreover, nucleation of cBN depends on Φi/ΦB, namely, the flux ratio of ion to boron, and requires accumulation of a certain surface state caused by ion bombardment effects, such as defects generation or densification.
Characteristics of spray pyrolytic ZnO:In thin films grown from zinc acetate and indium nitrate
Authors: Maldonado A. , de la L. Olvera M. , Asomoza R. , Zironi E. P. , Cañetas-Ortega J. , Palacios-Gómez J.
Published: July 2002

The structural, electrical and optical properties of indium doped zinc oxide films, grown by spray pyrolysis are reported. The starting solution was zinc acetate diluted in a mixture of isopropyl alcohol and water to 0.1 M, the doping solution was an aqueous solution of indium nitrate. The films were grown at substrate temperatures ranging from 675 K to 800 K. X-ray diffraction and micrographs indicate that the films are polycrystalline with textured surfaces having a predominance of the (002) and (101) reflections, depending on the substrate temperature. They have a resistivity as low as 6×10−5Ω m and a transmittance better than 85% in the visible range.
Optical and transport properties of amorphous and microcrystalline silicon films prepared by excimer laser assisted rf glow-discharge deposition
Authors: Roca i Cabarrocas P. , Layadi N. , Kunst M. , Clerc C. , Bernas H.
Published: July 2002

Hydrogenated amorphous and microcrystalline silicon films were deposited on glass substrates at 250 °C by combining rf glow discharge decomposition of silane–helium gas mixtures and ultraviolet laser irradiation on the surface of the growing film. The effect of the laser fluence on the optical and electrical properties of the films was investigated with combined in situ ellipsometry and ex situ techniques. Particular attention was paid to the properties of the films deposited at low and high laser fluences. At a low laser fluence, the resulting hydrogenated amorphous silicon films display a reduced defect density as compared to unirradiated ones. At laser fluences above the melting threshold, we obtain microcrystalline silicon films with a high surface roughness, as observed by scanning electron microscopy, and high electron mobility, as deduced from time resolved microwave conductivity measurements. The enhanced optical absorption produced by the roughness along with the high electron mobility make these films excellent candidates for photodetection and photovoltaic devices.
X-ray photoelectron spectroscopy of air-exposed C60 films: Origin of the O1s core peak
Authors: Onoe J. , Takeuchi K. , Ohno K. , Kawazoe Y.
Published: July 2002

X-ray photoelectron spectra of C60 films exposed to air of ca. 20% and 60% humidity at 23 °C for 1 h are presented. It was found that the O1s core peak appeared at a binding energy of 533.5 eV for the film exposed to air of ca. 60% humidity, while no peak corresponding to the O1s photoelectrons was observed for the film exposed to air of ca. 20% humidity. The binding energy of 533.5 eV for the O1s core peak is close to that of about 533 eV for the O1s core peak of solid H2O, while it is different from that of 537 eV for the O1s core peak of solid O2 on C60 film. These facts indicate that the O1s peak observed for the air-exposed C60 film was due to H2O molecules adsorbed on the film.
Radio frequency magnetron sputter deposition of CaF2 films
Authors: Dudney N. J.
Published: July 2002

Calcium fluoride films have been deposited onto unheated (<100 °C) substrates by low power rf magnetron sputtering of CaF2 targets using Ar and Ne process gases at pressures of 0.5–2.7 Pa, biased and floating substrate potentials, and various geometries of the substrate with respect to the source. The thickness and composition of the films are very sensitive to resputtering of the growing film. Uniform and stoichiometric films were most readily obtained on off-axis substrates using two sputter sources oriented with the targets facing each other. The films were found to be crystalline, have a fine textured microstructure, and to be transparent and highly resistive.
Enhanced Schottky barrier on InGaAs for high performance photodetector application
Authors: He L. , Costello M. J. , Cheng K. Y. , Wohlert D. E.
Published: July 2002

A low temperature (LT=77 K) processing technique was used for Schottky metal deposition on InGaAs. The Schottky barrier height of Ag/InGaAs contact processed at low temperature was found to be 0.64 eV. This value is more than two times higher than that of the barrier height of 0.30 eV obtained from the sample processed at room temperature (RT). The enhanced Schottky contacts are superior for the application on high performance semiconductor photodetectors. The current–voltage–temperature (I–V–T) measurements were conducted to study the current transport mechanism. Atomic force microscope was used to study the surface morphology correlating with the electrical properties. The LT metal showed cracked structure, which combined by islands, while the RT metal surface appeared to be more uniform with some sharp dots.
Comparison of x-ray magnetic circular dichroism at the L and M edges of Mo, Ru, Rh, and Pd
Authors: Tomaz M. A. , Lin Tao , Harp G. R. , Hallin E. , Sham T. K. , O’Brien W. L.
Published: July 2002

We present a survey of x-ray magnetic circular dichroism (XMCD) of the 4d elements Mo, Ru, Rh, and Pd at both the L and M absorption edges using, respectively, an InSb crystal monochromator and a toroidal grating monochromator. The relative merits of XMCD at each edge are examined, and we find that with the present apparatus, the L edge is clearly preferred for Pd, the M edge is preferred for Mo, while either edge is satisfactory for Rh and Ru.
Deep-submicron trench profile control using a magnetron enhanced reactive ion etching system for shallow trench isolation
Authors: Yeon Chung-Kyu , You Hyuk-Joon
Published: July 2002

One of the important issues for the deep-submicron shallow trench isolation process is profile control in the trench etch process for voidless gap filling with the chemical vapor deposition oxide. We examined the effects of some additive gases such as N2 or He–O2 (30% O2) on the trench slope to obtain an optimized trench profile with a commercial magnetron enhanced reactive ion etching system. It was found that the thickness of deposited film on the trench sidewall was highly related to the trench slope. As the film thickness increases, the trench profile becomes more tapered. The thickness of the sidewall film was directly proportional to the amount of the additive gases, N2 and He–O2. As the amount of He–O2 increases in the Cl2+HBr+He–O2 chemistry, the etch rate of silicon nitride decreases and the ratio of the silicon etch rate to the silicon nitride etch rate drastically increases. Scanning electron microscopy shows thick film deposits on the trench sidewall during the trench etch process. To know the chemical constituents in the deposited film on the sidewall, an angle-resolved x-ray photoelectron spectroscopy (XPS) was used. XPS results reveal that the deposited film on the trench sidewall is composed of SiOx in Cl2+HBr+He–O2 and SiOxNy in Cl2+HBr+N2. Cl or Br were not detected in our XPS measurements because the absorbed Cl or Br might react with water vapor to form HCl(g) or HBr(g) and grow SiOx when the samples are exposed to air. An aspect ratio dependence of the trench sidewall slope was observed. Usually the dense patterns are more vertical than the isolated patterns.
Ultrahigh-selectivity silicon nitride etch process using an inductively coupled plasma source
Authors: Wang Ying , Luo Leroy
Published: July 2002

A very high-selectivity silicon nitride etch process has been developed on an inductively coupled plasma etching system which uses a NF3/O2/NH3 (nonchlorine) chemistry. Etch selectivity of low-pressure chemical vapor deposition nitride to thermal oxide greater than 100:1 was achieved at a nitride etch rate of 500 Å/min. A NF3/O2 chemistry was optimized for nitride to oxide selectivity of about 12:1, with a nitride etch rate of 1200 Å/min. The addition of NH3 inhibits oxide etching thus enhancing selectivity. The net etch rate for oxide may be reduced to zero while maintaining a reasonably high etch rate for nitride thus resulting in essentially infinite selectivity. The process is stable, repeatable and creates no particles. A split lot test on device wafers against standard wet etch process demonstrates superior process and device performance.
Structural characteristics and hardness of zirconium carbide films prepared by tri-ion beam-assisted deposition
Authors: He Xiao-Ming , Shu Li , Li Hai-Bo , Li Heng-De , Lee S.-T.
Published: July 2002

Zirconium carbide (ZrC) films were prepared by using two Ar+ beams to sputter a zirconium target and a graphite target separately, and a third Ar+ beam to simultaneously bombard the growing film. The effects of the arrival rate ratio of zirconium to carbon (Zr/C) and the bombarding Ar+ energies of 0.1–15 keV on the formation, structure and properties of the films were investigated. It was found that although the Zr/C atomic ratio could be varied within a range of 0.45–1.26 without inhibiting the formation of crystalline ZrC, the increase of Zr/C will reduce the hardness and enhance the (220) orientation of ZrC films. The energy of bombarding Ar+ ions substantially influenced the crystallographic orientation and morphology of the deposited films. The experimental results disclosed that the ZrC films prepared by 800–1000 eV Ar+-assisted bombardment with a Zr/C ratio of 0.78–0.97 have a fine and compact structure, and hardness as high as 2800–3150 kgf mm−2.
Investigation of ice-solid interfaces by force microscopy: Plastic flow and adhesive forces
Authors: Pittenger Bede , Cook Debra J. , Slaughterbeck Clifford R. , Fain Samuel C.
Published: July 2002

The interaction between oxidized silicon atomic force microscope tips and vapor-deposited ice in a pure water vapor environment is studied using force curve measurements. The adhesive pull-off force and the indentation depth are approximately proportional to the maximum applied force for ice temperatures between −5 °C and −15 °C. A simple plastic flow model is used to deduce yield strengths comparable to previous macroscopic measurements at similar time scales (∼0.01 s). The rapid dynamics of ice surfaces above −20 °C allows the indentation to be partially filled in between force curves.
Quantitative determination of dielectric thin-film properties on product wafers using infrared reflection-absorption spectroscopy
Authors: Niemczyk Thomas M. , Zhang Lizhong , Haaland David M. , Radigan Kenneth J.
Published: July 2002

Process monitoring of borophosphosilicate glass (BPSG) dielectric thin films used in the manufacture of microelectronic devices is currently performed using multivariate calibration models developed from transmission infrared (IR) spectra of the films deposited on undoped monitor Si wafers. It would more be desirable to monitor the BPSG deposition on the actual product or device wafers. Because product wafers are opaque in the IR, reflection rather than transmission spectroscopy must be used to monitor the BPSG films deposited on product wafers. In this article, we demonstrate, for the first time, that IR reflection spectra of product wafers can be used to monitor the boron and phosphorus contents of the film and the film thickness to a precision that is comparable to that found for IR analysis of BPSG deposited on monitor wafers. The cross-validated standard errors of prediction of 0.11 wt %, 0.11 wt %, and 3 nm for B, P, and thickness, respectively, were achieved using multivariate partial least squares (PLS) models applied to the IR reflectance spectra obtained from reference product wafers. The prediction abilities were found to be independent of the position of the infrared spectrum on a given device and independent of which devices of the same structure were examined. The multivariate calibration models could be used to predict the B and P contents and film thickness of BPSG on device structures of different types and even for devices of different feature sizes if the PLS models were adjusted for slope and intercept differences. Therefore, the time and expense of generating calibrations for new device structures can be greatly reduced by the use of a small number of reference samples of the new devices to estimate the required slope and intercept adjustments for the models.
Chemical downstream etching of tungsten
Authors: Blain M. G. , Jarecki R. L. , Simonson R. J.
Published: July 2002

The downstream etching of tungsten and tungsten oxide has been investigated. Etching of chemical vapor deposited tungsten and e-beam deposited tungsten oxide samples was performed using atomic fluorine generated by a microwave discharge of argon and NF3. Etching was found to be highly activated with activation energies approximated to be 6.0±0.5 kcal/mol and 5.4±0.4 kcal/mol for W and WO3, respectively. In the case of F etching of tungsten, the addition of undischarged nitric oxide (NO) directly into the reaction chamber results in the competing effects of catalytic etch rate enhancement and the formation of a nearly stoichiometric WO3 passivating tungsten oxide film, which ultimately stops the etching process. For F etching of tungsten oxide, the introduction of downstream NO reduces the etch rate.
A (NH4)2Sx-treated InSb(001) surface studied by using x-ray photoelectron spectroscopy, low-energy electron diffraction, and inverse photoemission spectroscopy
Authors: Ichikawa S. , Suzuki Y. , Sanada N. , Utsumi N. , Yamaguchi T. , Gong X. Y. , Fukuda Y.
Published: July 2002

A (NH4)2Sx-treated InSb(001) surface has been studied by using x-ray photoelectron spectroscopy, low-energy electron diffraction, and inverse photoemission spectroscopy (IPES). A thick sulfide layer is formed on the as-treated and annealed surfaces at less than about 400 °C. The thickness of the sulfide layer is estimated to be about 6–7 ML. Sulfur is bonded to both In and Sb in the as-treated surface layer although it is bonded only to indium in the layer annealed at more than 310 °C. A (2×1) structure appears for the treated surface annealed at 310 °C. The binding energy shift (−0.3 eV) of In 3d5/2 and Sb 3d3/2 is found for the (2×1) surface. The IPES spectra show that the density of states of unoccupied dangling bonds for surface indium is reduced by the (NH4)2Sx treatment. The binding energy shift and structure of the sulfide layer are discussed.
Audio-frequency glow discharge for plasma chemical vapor deposition from organic compounds of the carbon family
Authors: Tyczkowski J.
Published: July 2002

An audio-frequency (af) (10–100 kHz) glow discharge has been used for plasma chemical vapor deposition of thin films from organic compounds of the carbon family. It has been realized employing a recently designed reactor, equipped with three electrodes—a small electrode on which films are deposited, and two main electrodes sustaining a glow discharge. The small electrode and one main electrode are connected by a variable capacitance C. It has been found that small changes of C can cause a drastic change in the electronic properties of deposited films. This effect, attributed to a transition between the amorphous insulator (a-I) and amorphous semiconductor (a-S), is discussed for hydrogenated carbon–silicon, carbon–germanium, carbon–tin, and carbon–lead films produced from adequate organometallic compounds. To better understand the deposition process in the reactor, the electrical characteristics of model argon plasma have been investigated by means of a Langmuir single probe movable in the space between the reactor electrodes. Both af potentials of the plasma and typical current–voltage characteristics have been measured. It has been found that energetic conditions of the plasma, and consequently, the plasma chemistry, are independent of C. Changes of C have, however, influence on the ion bombardment process taking place in the vicinity of the small electrode. The ion impact energy Emax has been roughly estimated and a relation Emax∝ln C is found. The calculated values of Emax, which change from almost zero to several tens of electron volts, are in a good agreement with results of an experiment performed in the reactor with argon sputter etching of a gold film.