Showing papers on "Tungsten published in 1983"

Tungsten-183 NMR: a complete and unequivocal assignment of the tungsten-tungsten connectivities in heteropolytungstates via two-dimensional tungsten-183 NMR techniques

Abstract: Utilisation de deux sequences spectroscopiques RMN a deux dimensions, de type COSY, et INADEQUATE, pour determiner sans ambiguite une attribution des liaisons tungstene-tungstene dans les heteropolytungstates

Wafer-scale laser pantography: Fabrication of n-metal-oxide-semiconductor transistors and small-scale integrated circuits by direct-write laser-induced pyrolytic reactions

Abstract: A complete set of processes sufficient for manufacture of n‐metal‐oxide‐semiconductor (n‐MOS) transistors by a laser‐induced direct‐write process has been demonstrated separately, and integrated to yield functional transistors. Gates and interconnects were fabricated of various combinations of n‐doped and intrinsic polysilicon, tungsten, and tungsten silicide compounds. Both 0.1‐μm and 1‐μm‐thick gate oxides were micromachined with and without etchant gas, and the exposed p‐Si [100] substrate was cleaned and, at times, etched. Diffusion regions were doped by laser‐induced pyrolytic decomposition of phosphine followed by laser annealing. Along with the successful manufacture of working n‐MOS transistors and a set of elementary digital logic gates, this letter reports the successful use of several laser‐induced surface reactions that have not been reported previously.

Properties of low-pressure CVD tungsten silicide for MOS VLSI interconnections

Abstract: Low-pressure chemical vapor deposition of tungsten silicide has been done and the properties of the deposited films have been studied to determine the process compatibility and suitability to form gate electrodes and interconnections in MOS VLSI applications. The silicide was deposited on single-crystal silicon and on oxidized silicon with and without a coating of polycrystalline silicon film. Auger analysis of the As-deposited films showed absence of any contaminants in it. X-ray diffraction and transmission electron microscopy showed that As-deposited films were microcrystalline with grains smaller than 30 A and upon annealing became polycrystalline WSi 2 with hexagonal structure at 500°C and tetragonal structure at or above 600°C with a corresponding decrease in resistivity from 600-900 µΩ . cm to 35-60 µΩ . cm depending upon anneal temperature and time. No appreciable change in the thickness of the silicide was found during the high-temperature anneals. Silicon-rich silicide films remained stable, smooth, and free of cracks through high-temperature anneals and oxidations, and their adherence to the wafer remained excellent. On the other hand, metal-rich films had overall inferior properties. Thermal oxidation of WSi 2 on polysilicon in dry oxygen in the temperature range of 900 to 1100°C was found to be similar to that of silicon except the linear regime of oxidation was extremely rapid and the entire process could be modeled by a parabolic equation X^{2) = Bt with an activation energy of 1.7 eV. MOS capacitors were fabricated with silicide and polycide gate electrodes. Polysilicon thickness variation from 0 to 5000 A had no adverse effect on the electrical characteristics or mechanical integrity of the devices. In all cases, low values of N f (1 × 1010-7 × 1010cm-2) and N it ( \sime 8 MV/cm) were obtained.

Preparation of VO 2 thin film and its direct optical bit recording characteristics

Abstract: Vanadium dioxide (VO2) film which has nearly the same transition point as single crystal has been obtained by reactive evaporation of vanadium on glass and subsequent annealing in N2 gas. Relations between optical properties of V02 film and its preparation conditions are presented. We made optical direct bit recording on V02 film using a laser diode as the light source. The threshold recording energy and bit density are 2 mJ/cm 2 and 350 bits/mm, respectively. We also made tungsten doping to lower the V02 film transition temperature.

High temperature hardness of tungsten carbide

Abstract: The effect of crystallographic orientation and test temperature on hardness of WC single crystals was investigated along with the hot hardness of poly crystalline tungsten carbide. Also investigated was the effect of carbide grain size and the amount of binder phase on the hot hardness of some cemented tungsten carbides. The hot hardness of single crystal WC on all major crystallographic orientations evaluated decreases very rapidly for increasing temperature, and the single crystal hardness on its hardest orientation is only about half of the polycrystalline material depending on the test temperature. Because of its polycrystalline character, some cobalt bonded cemented tungsten carbides can be harder than single crystal WC over some intermediate temperature range.

Physical and electrochemichromic properties of rf sputtered tungsten oxide films

Abstract: The physical and electrochemical coloration characteristics of tungsten oxide films rf sputtered from a compressed powder WO3 target have been investigated. Oxide films with 3600–9800 A thickness were deposited on substrates maintained at 200 °C at a total pressure of 0.5–8×10−2 Torr in Ar gas or an Ar‐0.5‐50% O2 gas mixture. Physical properties of the oxide films depend on the oxygen concentration and total pressure of the sputtering atmosphere. The films prepared at 4×10−2 Torr in a mixture of Ar‐0.5‐20% O2 gas are transparent and amorphous, and their electrical resistivity ranges from 6.5×108 to 2.4×1011 Ω cm. The films prepared at pressures between 4 and 6×10−2 Torr in an Ar‐50% O2 gas mixture are transparent, and have crystallites with a composition of WO3. The films prepared at 1×10−2 Torr in a mixture of Ar‐0.5 and 5.0% O2 gas are blue colored and transparent, respectively, and these films are crystallites with a composition of WO2.83. Electrochemichromic properties of the rf sputtered tungsten oxi...

The properties of tungsten processed by chemically activated sintering

Abstract: Two tungsten powders have been treated with small concentrations of sintering activators to provide for enhanced low temperature sintering. The experimental study focused on the determination of the processing effects on properties such as sintered density, grain size, hardness, and strength. Variables in the plan included tungsten particle size, type of activator, amount of activator, compaction pressure, and sintering temperature. The sintered density is found to have a dominant effect on strength and hardness. The various processing variables are analyzed in terms of their effects on density. At high sintered densities, grain growth acts to degrade the strength. Additionally, the nature of the sintering activator influences the fracture strength. In this study optimal strength occurred with a 0.7 μm tungsten powder treated with 0.29 wt pct Ni, sintered at 1200 °C for one hour. The resulting density was 18.21 g/cm3, with aR A hardness of 69 and a transverse rupture strength of 460 MPa.

Enhanced adhesion from high energy ion irradiation

Abstract: We have found that irradiation of a variety of thin film-substrate combinations by heavy ion beams at energies of mega-electronvolts per atomic mass unit will produce a remarkable enhancement in the adherence of the film. For example, gold films can be firmly attached to soft materials such as Teflon using a 1 MeV beam of protons (10^(14) cm^(−2)) or helium ions (10^(13) cm^(−2)) and to harder materials such as silicon (10^(15) cm^(−2)), quartz (2 × 10^(15) cm^(−2)) and tungsten (2 × 10^(14) cm^(−2)) with 0.5 MeV a.m.u.^(−1) beams of fluorine or chlorine ions. In the case of metal films on semiconductors a low resistance contact results. The mixed layer at the interface is observed to be quite thin (approximately 50 A or less); for silver on silicon electron diffraction and imaging studies of the interface region reveal the presence of crystalline silver compounds.

Segregation to interphase boundaries in liquid-phase sintered tungsten alloys

Abstract: Scanning Auger electron spectroscopy has been used to examine the distribution of impurity elements on the fracture surfaces of liquid-phase sintered W-Ni-Cu and W-Ni-Fe alloys. On the interphase boundaries between the fcc Ni-based matrix phase and the tungsten particles, segregation levels of ~0.4 and ~0.2 monolayers of phosphorus have been observed in as-sintered, furnace-cooled specimens of W-Ni-Cu and W-Ni-Fe, respectively. The phosphorus is homogeneously distributed but at fracture adheres preferentially to the matrix phase. High temperature heat treatment (1350 °C) followed by water quenching reduces significantly the phosphorus segregation and improves the degree of cohesion across these boundaries. Segregated sulfur is detected on both sides of the interphase boundaries after fracture. The sulfur is much less uniformly distributed than the phosphorus, and its segregation level increases in the heat treated specimens. Copper also segregates to the interphase boundaries during the heat treatment of W-Ni-Cu specimens, but no equivalent segregation of iron was observed in the W-Ni-Fe system. The boundaries developed between adjacent tungsten particles are free of impurity contamination in both alloy systems but have a segregated layer of nickel.

GaAs Light Emitting Diodes Fabricated on SiO2/Si Wafers

Abstract: GaAs LEDs have been successfully realized on thermally oxidized Si wafers. Ge layers were recrystallized on tungsten coated SiO2/Si wafers and used as substrates for GaAs epitaxial growth. Light emission of around 9000 A was observed at room temperature.

A planar metallization process—Its application to tri-level aluminum interconnection

Abstract: A planar metallization process has been proposed, where contact windows or via holes of a high aspect ratio are refilled with tungsten by selective CVD enloloying WF 6 . In tungsten selective CVD, an appropriate choice of substrate material and surface cleaning prior to tungsten deposition is a key factor to success. For selective deposition onto Al, Al surface is coated with MoSi 2 thin layer, and contact resistivities of refilling tungsten with n+Si and MoSi 2 coated Al are comparable to those of conventional Al metallization. Combining a interlevel insulator surface planarization process and a planar metallization process, a tri-level aluminum interconnection process of 1 micron feature size has been constructed, which has a scheme extensive to submicron feature size.

On the mechanism for improved passivation by additions of tungsten to austenitic stainless steels

Abstract: In order to elucidate the role of W in improving the passivity of austenitic stainless steels, anodic polarization curves and X-ray photoelectron spectra have been obtained for pure W and ...

A quantitative study of vacancy defects in quenched tungsten by combined field-ion microscopy and electrical resistometry

Abstract: A study of quenched, high-purity tungsten has been carried out with a combination of field-ion microscopy (FIM) and electrical resistivity measurements. it was concluded that the quenched-in vacancy defects observed by FIM were monovacancies and nearest-neighbor divacancies. From the partitioning during quenching between these two species, a divacancy binding enthalpy H/sub 2v/sup b/ approx. = 0.7 eV was deduced. A monovacancy resistivity of 7 x 10/sup -4/ ..cap omega.. cm was obtained from the combined measurements. The quenched-in vacancy concentrations directly measured by FIM are consistent with previous results, if the total vacancy concentration at the melting temperature of tungsten (3695 K) is about 3 x 10/sup -4/ and the monovacancy formation enthalpy and entropy are 3.6 eV and 3.2 k, respectively. Results are discussed in terms of the atomic-defect mechanisms for self-diffusion in tungsten. 6 figures, 4 tables.

Kinetics of hydrogen absorption by titanium, tantalum, tungsten, iron and palladium films with and without oxygen preabsorption at 300 K

Abstract: The hydrogen absorption rates of titanium, tantalum, tungsten, iron and palladium films 15–20 nm thick were measured at room temperature and hydrogen pressures between 10−9 and 10−4 mbar using the volumetric method. Films with clean surfaces absorb gas amounts in the concentration ranges corresponding to hydride formation for titanium and tantalum and equivalent to about one monolayer of hydrogen for tungsten, iron and palladium with reaction probabilities in the range 1–10−4. The reaction rates are strongly reduced if the film surface is coated with oxygen at thicknesses equivalent to several monolayers. Iron and palladium films precoated with oxygen show an H2O partial pressure peak which indicates that the oxygen sorption layer is reduced by the formation of H2O during exposure to hydrogen.

Thick film conductor compositions

Abstract: A copper-containing thick film conductor composition comprising a mixture of finely divided particles of (a) a conductive material containing copper metal, (b) inorganic binder and (c) 0.2-5% wt. of a noncuprous metal selected from the group consisting of tungsten, molybdenum, rhenium and alloys and mixtures thereof all dispersed in organic medium. The metal particles must be within certain narrow ranges of particle size.

Package comprising a composite metal body brought into contact with a ceramic member

Abstract: In a package comprising a ceramic member so as to accommodate a semiconductor device, a composite metal body which comprises copper and either one of tungsten and molybdenum is brought into contact with the ceramic member. The composite metal body is provided by impregnating molten copper into a porous block of tungsten or molybdenum and changeable in a thermal expansion coefficient and a thermal conductivity by controlling an amount of copper. The composite metal block may be used as a support for supporting the semiconductor device and/or as a heat sink for dissipating heat radiated from the semiconductor device. Preferably, the composite metal body comprises, by weight, 1-30% of copper and 99-70% of tungsten or molybdenum.

Powder comprising coated tungsten grains

Abstract: A heterogenous powder comprising particles of tungsten grains with a diameter of less than 1 μm with a binder sponge-like coating of at least one metal selected from the group consisting of nickel, copper, silver, iron, cobalt, molybdenum and rhenium with a particle diameter of 10 to 50 μm, a process for the preparation thereof, method of forming sintered elements therefrom and the elements produced thereby being useful as penetrating projectiles.

Effect of vacuum-treatment on mechanical properties of W-Ni-Fe heavy alloy

Abstract: The effect of heat-treatment in vacuum and hydrogen on the ductility and UTS of the sintered 96W-2.8Ni-1.2Fe (by wt%) heavy alloy has been studied. The elongation of the as-sintered alloy is about 8%, but after a few minutes of heat treatment in vacuum at 800° C it increases markedly to about 19%. When the sintered specimen is heat-treated in vacuum at 600° C, the elongation increases rapidly with time, reaching 20% after about 10 min. The values of UTS also increase after vacuum treatment. Heat treatment in hydrogen, however, shows no change in mechanical properties from the as-sintered state. The effect of vacuum treatment is thus attributed to the removal of hydrogen embrittlement. Based on the hydrogen diffusion model, a practical guide line is suggested for determining the optimum vacuum treatment conditions. The scanning electron micrographs of the fracture surfaces show that hydrogen weakens mainly the interface between tungsten grains and matrix.