Showing papers on "Tungsten published in 2000"

Method of forming metal layer using atomic layer deposition and semiconductor device having the metal layer as barrier metal layer or upper or lower electrode of capacitor

Abstract: A method of forming a metal layer having excellent thermal and oxidation resistant characteristics using atomic layer deposition is provided. The metal layer includes a reactive metal (A), an element (B) for the amorphous combination between the reactive metal (A) and nitrogen (N), and nitrogen (N). The reactive metal (A) may be titanium (Ti), tantalum (Ta), tungsten (W), zirconium (Zr), hafnium (Hf), molybdenum (Mo) or niobium (Nb). The amorphous combination element (B) may be aluminum (Al), silicon (Si) or boron (B). The metal layer is formed by alternately injecting pulsed source gases for the elements (A, B and N) into a chamber according to atomic layer deposition to thereby alternately stack atomic layers. Accordingly, the composition ratio of a nitrogen compound (A—B—N) of the metal layer can be desirably adjusted just by appropriately determining the number of injection pulses of each source gas. According to the composition ratio, a desirable electrical conductivity and resistance of the metal layer can be accurately obtained. The atomic layers are individually deposited, thereby realizing excellent step coverage even in a complex and compact region. A metal layer formed by atomic layer deposition can be employed as a barrier metal layer, a lower electrode or an upper electrode in a semiconductor device.

Slurries for chemical mechanical polishing

Abstract: Novel slurries for the chemical mechanical polishing of thin films used in integrated circuit manufacturing. A tungsten slurry of the present invention comprises an oxidizing agent, such as potassium ferricyanide, an abrasive such as silica, and has a pH between two and four. The tungsten slurry of the present invention can be used in a chemical mechanical planarization process to polish back a blanket deposited tungsten film to form plugs or vias. The tungsten slurry can also be used to polish copper, tungsten silicide, and titanium nitride. A second slurry, which is a 9:1 dilution of the tungsten slurry is ideal for chemical mechanical polishing of titanium nitride films. A third slurry of the present invention comprises a fluoride salt, an abrasive such as silica and has a pH≦8. The third slurry can be used to polish titanium films.

Residual stress, microstructure, and structure of tungsten thin films deposited by magnetron sputtering

Abstract: The residual stress and structural properties of tungsten thin films prepared by magnetron sputtering as a function of sputtering-gas pressure are reported. The films were analyzed in situ by a cantilever beam technique, and ex situ by x-ray diffraction, cross-sectional transmission electron microscopy (TEM), x-ray photoelectron spectroscopy, electron energy-loss spectrometry, and energy-filtered electron diffraction. It is found that the residual stress, microstructure, and surface morphology are clearly correlated. The film stresses, determined in real time during the film formation, depend strongly on the argon pressure and change from highly compressive to highly tensile in a relatively narrow pressure range of 12–26 mTorr. For pressures exceeding ∼60 mTorr, the stress in the film is nearly zero. It is also found that the nonequilibrium A15 W structure is responsible for the observed tensile stress, whereas the stable bcc W or a mixture of bcc W and A15 W are in compression. Cross-sectional TEM eviden...

A fiber-optic evanescent-wave hydrogen gas sensor using palladium-supported tungsten oxide

Abstract: A new optical-fiber hydrogen sensor has been developed. The sensor utilizes the absorption change of the evanescent field in the clad region. The platinum- or palladium-supported tungsten oxide was used as sensing media. Two different approaches were adopted for the fiber fabrication. One used Pd/WO3 containing silicone resin as the clad. The other utilized the sol–gel process to form a thin Pd/WO3 clad. In the presence of hydrogen, strong evanescent-wave absorption was observed as a result of the formation of tungsten bronze. The sensor sensitively and immediately responded to hydrogen. It was found that the characteristics of the sensor were easily controlled by the amount of catalysts. The sensor developed in this study has potential to measure the spatial distribution along the fiber line, unlike the traditional hydrogen sensors that measure the concentration of a certain spatial point.

Manufacturing method for semiconductor metalization barrier

Abstract: A semiconductor metalization barrier, and manufacturing method therefor, is provided which is a stack of a cobalt layer and cobalt tungsten layer deposited on a copper bonding pad.

Study of the Temperature-Programmed Reaction Synthesis of Early Transition Metal Carbide and Nitride Catalyst Materials from Oxide Precursors

Abstract: The synthesis of high surface area carbide and nitride materials from binary and ternary oxides of vanadium, niobium, tantalum, molybdenum, and tungsten, suitable for use as catalysts for a wide ra...

Nanocrystalline Tungsten Oxide Thin Film: Preparation, Microstructure, and Photochromic Behavior

Abstract: A nanocrystalline tungsten oxide photochromic thin film was prepared by colloid chemistry method. The microstructure, phase transition involved in the solution process, photochromic behavior, and mechanism of the film were investigated by means of transmission electron microscope, x-ray diffraction, ultraviolet-visible absorption spectra, and x-ray photoelectron spectra. It was found that the particle size and crystallinity of the thin film could be easily controlled by adjusting the concentration of oxalic acid in the colloid solution of tungsten oxide hydrate. With the increase of the oxalic acid concentration, the size of nanoparticles in the film decreased sharply, and meanwhile, a blue shift of the absorption peaks caused by the quantum size effect was observed accordingly. With the increase of the pH in the solution, tungsten oxide hydrate was gradually transformed into an oxided 12-tungstate with Keggin structure, which led to the change of photochromic property of the films. The photochromism of the film is believed to be due to the electron transfer between the different valence states of tungsten ions located in adjacent sites.

Process for depositing a tungsten-based and/or molybdenum-based layer on a rigid substrate, and substrate thus coated

Abstract: The present invention is directed to a process for depositing at least one layer ( 3 ) based on tungsten and/or on molybdenum by chemical vapor deposition on a non-conductive substrate ( 1 ), such as glass, ceramic, glass-ceramic, or polymer, which includes providing at least one tungsten- and/or molybdenum-containing precursor in the form of a metal halide and/or of an organometallic compound, and at least one reducing agent, such as hydrogen or silane, to form the at least one metal layer. The present invention also relates to the substrate obtained by the preceding process and its applications, especially for producing a glazing, mirrors, or emissive screens.

Plasma processing of tungsten using a gas mixture comprising a fluorinated gas and oxygen

Abstract: A method and apparatus for etching of a substrate comprising both a polysilicon layer and an overlying tungsten layer. The method comprises etching the tungsten layer in a chamber using a plasma formed from a gas mixture comprising a fluorinated gas (such as CF4, NF3, SF6, and the like) and oxygen.

High temperature tungsten etching process

Abstract: A method of etching a tungsten film, comprising the steps of supporting a semiconductor substrate having a tungsten film thereon on a substrate support in an interior of a plasma etcher, supplying process gas to the interior of the plasma etcher, energizing the process gas into a plasma state, etching the tungsten film by exposing the substrate to the plasma, and heating the substrate to a temperature of at least 100° C. during the etching step. The etching step can include a low temperature main etch below 100° C. followed by a high temperature overetch above 100° C., the process gas including a fluorine containing gas during the main etch and a chlorine containing gas during the overetch. The tungsten film can be located over a dielectric film which serves as a stop layer during the etching step. The tungsten film can be pure tungsten and the dielectric layer can be a silicon oxide film having a thickness of 200 Å or less.

Effect of target material on deposition and properties of metal-containing DLC (Me-DLC) coatings

Abstract: Metal containing diamond-like carbon (Me-DLC) coatings were prepared by magnetron sputter deposition using tungsten, tungsten carbide, niobium and titanium as target materials. An essential parameter for the process characterization is the target voltage. The substrate heating during the film growth depends on the target material. For the tungsten target, the contribution of energetic neutrals to the heat flux is quite high. From the viewpoint of resistance to abrasive wear, the best properties were found for W-DLC. The Nb-DLC coatings have an intermediate wear rate but offer the lowest friction coefficients and a high performance under adhesive wear loading. All Me-DLC coatings investigated in this study exhibit clearly higher wear rates than metal-free DLC films prepared by a radio frequency glow discharge technique. Metallic intermediate layers allow the preparation of coatings with a very good adhesion.

Prediction of properties of free burning arcs including effects of ambipolar diffusion

Abstract: A method is described to predict the two-dimensional distributions of temperature, velocity and potential of free burning arcs and their electrodes for cathodes of tungsten and thoriated tungsten. The effects of non-equilibrium due to the ambipolar diffusion of charged particles are included for the calculation of the plasma electrical conductivity. The electron diffusion current is explicitly included in the solution of the current continuity equation. The plasma for the arc and the electrode sheath regions is treated as a continuum, so that the thickness of the non-equilibrium regions near the electrodes is determined within the model, depending upon the arc current and the arc and electrode configuration. This new treatment allows the calculation of the negative anode fall that may occur across the anode sheath when the electron diffusion current near the anode surface becomes larger than the total arc current. For a thoriated tungsten cathode we take the work function for cooling by electron emission to be that of tungsten, as, for small percentages of thoria in tungsten, cooling effects from electrons passing through the interfaces for tungsten-thoria and then thoria-plasma will add up to be that of a tungsten-plasma interface. Calculations have been made for arcs in argon at currents between 2.5 A and 200 A. For currents above 120 A, we calculate the anode fall voltage to be negative, being -2 V at 200 A. For currents less than 50 A, non-equilibrium effects in the plasma extend across the whole arc and electron number densities can be several orders of magnitude below the values for local thermodynamic equilibrium. Calculated arc voltages, arc temperatures and electrode temperatures are in agreement with experimental measurements to within 20%.

Pore Surface Functionalization of MCM-48 Mesoporous Silica with Tungsten and Molybdenum Metal Centers: Perspectives on Catalytic Peroxide Activation

Abstract: The pore surface of MCM-48 mesoporous silica was functionalized with tungsten and molybdenum metal centers by the anhydrous reaction of metal alkoxides with surface silanol groups. Resulting metal−oxo species were attached via covalent M−O−Si bonds as confirmed with photoacoustic (PAS)-FTIR. Diffuse reflectance UV−visible spectroscopy indicates that the metal oxo groups are predominantly comprised of tetrahedral and octahedral coordinated monomers. MCM-48 grafted with Mo and W is active for brominating phenol red with hydrogen peroxide at neutral pH in a manner similar to Ti−MCM-48, as we reported earlier. The rates of bromination for Mo, W, and four other metals, after normalization for metal concentration, measured as absorption peak intensities of the resultant bromophenol blue, are as follows: 50:46:16:2.8:1:0 W:Mo:Ti:Zr:V:Re. The different rates of reactivity, and hence the general degree of metal−peroxo activation, can be explained on the basis of size, charge, coordination sphere, and electronegat...

Composition, residual stress, and structural properties of thin tungsten nitride films deposited by reactive magnetron sputtering

Abstract: Thin tungsten nitride ( WN x ) films were produced by reactive dc magnetron sputtering of tungsten in an Ar–N 2 gas mixture. The effects of the variation of nitrogen partial pressure on the composition, residual stress, and structural properties of these films as well as the influence of postdeposition annealing have been studied. The films were analyzed in situ by a cantilever beam technique, and ex situ by x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, x-ray diffraction, and transmission electron microscopy(TEM). It was found that at N concentrations below 8 at. %, the films (typical 150 nm in thickness) were essentially bcc α-W. An amorphous phase was observed in the range of about 12–28 at. % N. When N concentrations reached ∼32 at. % or above, a single-phase structure of W 2 N was formed. Annealing of the as-deposited films resulted in crystallization of the amorphous or an improved crystallinity of the W 2 N structure, which was related to the N concentration. Stresses of all W and WN x films were compressive. As the N concentration was increased, the stress decreased and reached its lowest value for amorphous samples near 20 at. % N. Past this point, the compression of films rose again. These results can be ascribed to structural changes induced by the pressure-dependent variation in the average energy of particles bombarding the film during deposition. Cross-sectional TEM studies showed that all crystalline WN x films had columnar microstructures. The average column width near stoichiometry of W 2 N was ∼20±5 nm near the film surface.

Oxidation and dissolution of tungsten carbide powder in water

Abstract: The oxidation and dissolution of tungsten carbide powder dispersed in water was investigated using X-ray photoelectron spectroscopy (XPS) and leaching studies. We found that the WO 3 surface layer on the oxidised tungsten carbide powder dissolves readily at pH > 3 with the tungsten concentration increasing linearly with time. Adding cobalt powder to the tungsten carbide suspension resulted in a significant reduction of the dissolution rate at pH 3 solution chemistry and the Co 2+ adsorption at oxide/water interfaces.

Microstructure and mechanical properties of mechanically alloyed and solid-state sintered tungsten heavy alloys

Abstract: The mechanical properties of solid-state sintered 93W‐5.6Ni‐1.4Fe tungsten heavy alloys fabricated by mechanical alloying were investigated. Blended W, Ni and Fe powders were mechanically alloyed in a tumbler ball mill at a milling speed of 75 rpm employing a ball-to-powder ratio of 20:1 and a ball filling ratio of 15%. A nanocrystalline size of 16 nm and fine lamellar spacings of 0.2 mm were obtained in mechanically alloyed powders at a steady state milling stage. Mechanically alloyed powders were consolidated into green compacts and solid-state sintered at 1300°C fo r1hi n ahydrogen atmosphere. The alloys sintered from mechanically alloyed powders showed fine tungsten particles (about 3 mm in diameter) and a relative density above 99%. The volume fraction of the matrix phase was 11% and the tungsten:tungsten contiguity was determined to be 0.74. The alloys exhibited high yield strengths (about 1100 MPa) due to their fine microstructures, but exhibited reduced elongation and impact energy due to a large area fraction of tungsten:tungsten boundaries and the low volume fraction of matrix phase. © 2000 Elsevier Science S.A. All rights reserved.

Effect of aging treatments on microstructure and impact properties of tungsten substituted 2205 duplex stainless steel

Abstract: The effects of partial substitution of tungsten for molybdenum on the microstructure and impact properties in 22Cr–5Ni–3Mo (wt-%) duplex stainless steel (DSS) have been investigated following aging heat treatments in the temperature range 600–1000°C. During aging the intermetallic σ and χ phases were precipitated, and the impact toughness was significantly decreased with an increase in the σ phase content. The χ phase had been precipitated on the α/γ boundary in the early stages of aging. Ferrite and χ phases in tungsten substituted duplex stainless steel contain a large amount of tungsten, and their decomposition rates are much lower compared with those in steel containing only molybdenum. Consequently, the precipitation of the σ phase is retarded in tungsten substituted DSSs, which results in high impact toughness. However, after aging for a long time, the α and χ phases transformed to the σ and austenite phases in the tungsten substituted steels, and the steels showed low impact toughness.

Electroless Silver and Silver with Tungsten Thin Films for Microelectronics and Microelectromechanical System Applications

Abstract: In this study we present the results of electroless deposition of silver (Ag) and silver tungsten [Ag(W)] layers on Si, intended for application in microelectronics and microelectromechanical systems (MEMS) technology. Silver has excellent resistivity but its thin-film properties and its vulnerability to corrosion may cause a problem. In this work we present a novel Ag(W) type of layer that has improved thin-film properties, such as resistivity and surface roughness, and can serve as both barrier layer and capping layer for corrosion protection of the Ag thin films. The thin-film composition was studied as a function of the deposition parameters. We found the presence of tungsten, up to 3.1 atom %, and oxygen, up to 8 atom %, in addition to the silver atoms. We also studied the thin-film morphology using atomic force microscopy and scanning tunneling microscopy imaging of the surface after each process step. Finally, we discuss the possible mechanisms for the deposition of Ag(W ).

Mechanical properties of hard chromium tungsten nitride coatings

Abstract: Due to its excellent oxidation and wear resistance, CrN is a prominent material for protective coatings. Still, its comparatively low hardness prevents CrN from being widely used in industrial applications. Thin films of Cr 1− x W x N y with 0≤ x ≤1 were deposited on silicon, glass and steel substrates by reactive r.f. magnetron sputtering. The B1-NaCl phase is the only phase detected. In tungsten-rich films the compressive residual stress increases linearly with increasing tungsten content, but films with a high chromium content show tensile stresses. The morphology, examined by cross-section scanning electron microscopy, changed with increasing tungsten content from a columnar to a fine-grained microstructure. Hardness values, measured by nanoindentation, show a steep increase in hardness with only small additions of tungsten (hardness increases by 85% at a tungsten content of 10%). The maximum hardness value was measured for WN 0.7 (30 GPa). The ternary Cr 1− x W x N y films with 0.1≤ x ≤0.8 and 0.8≤ y ≤1 were significantly harder (29–24 GPa) compared to CrN (13 GPa). In scratch tests with progressively increasing load, the films prove to have good adhesion and wear resistance, although some cracking is observed in films with tensile residual stress. In multi-pass scratch tests at low load, brittle flank wear is observed in films with moderate to high tungsten contents, while the softer CrN film exhibit cracks in the wear track.

Tribological properties, phase generation and high temperature phase stability of tungsten- and vanadium-oxides deposited by reactive MSIP-PVD process for innovative lubrication applications

Abstract: The tungsten and vanadium oxides are promising to be usable as solid lubricants at elevated temperatures because of their ability to form oxygen deficient Magneli-phases. As a matter of fact, metal-oxides are interesting for tribological insets at atmospheric conditions because of their expected oxidation stability and low adhesion. The study reports about the deposition of tungsten and vanadium oxides in a reactive d.c. mode by the MSIP- (Magnetron Sputtering Ion Plating) PVD process and especially about the influence of the oxygen content in the sputtering atmosphere as well as the deposition temperature on the phase generation. A simplified ‘sputtering phase diagram’ of the binary systems V–O and W–O as a function of the deposition temperature (378–650 K) and the oxygen content (0–50%) was determined. Furthermore, it was shown that the tested vanadium-oxides are phase stable up to 878 K and the tungsten-oxides up to 1100 K (measured in a high-temperature XRD facility). Additionally tribological properties of the deposited oxide coatings, like the friction coefficient vs. steel, will be presented. For polished and WOx coated samples a friction coefficient of μ≈0.2 against steel was measured at room temperature. The coatings were analyzed by various testing methods to characterize the tribological, mechanical and structural properties, like SEM, nanoindentation, (high-temperature)-XRD and pin-on-disk.