A novel metallization for aluminum nitride substrates to package silicon carbide integrated circuits for use at temperatures up to 600°C was investigated. Chemical equilibrium calculations were used to determine the chemical compatibility of several refractory and transition metal disilicides with AIN. Tungsten disilicide, niobium disilicide, and titanium disilicide were selected for thin film deposition studies. WSi2, NbSi2, and TiSi2 thin films were deposited by RF sputtering on AIN substrates and heat treated at 900°C, 1000°C, and 1200°C in an argon atmosphere. Sheet resistivities were measured and interface stabilities and structures were characterized by scanning and transmission electron microscopy imaging, electron diffraction, and energy dispersive x-ray microanalysis spectroscopy. The results show that metal silicides appear to be promising as metallization for aluminum nitride for use at temperatures above 600°C.

This paper reports a pressure-temperature phase diagram for BaSi2 and evaluates the electrical resistivity of orthorhombic, cubic and trigonal BaSi2. In-situ X-ray diffraction measurements revealed the transition sequence of cubic and trigonal BaSi2 from orthorhombic BaSi2 at high pressures and high temperatures. The electrical resistivity measurements of three polymorphs show that the electrical properties depend on the crystal structure: orthorhombic BaSi2is an n-type semiconductor as previously reported; cubic BaSi2is an n-type semiconductor; trigonal BaSi2is a hole metal that shows superconductivity with an onset temperature of 6.8K.

The potential application of epitaxial Si1−xGex, on Si in electronic and optoelectronic devices has led to an increased study of metal - Si1−xGex interaction and barrier height control technique. In this paper, we report the epitaxial growth of Si1−xGex on Si and the Schottky barrier formation processing. The Si1−xGex (x=0.17 and 0.20) layers were grown by rapid radiant heating, very low pressure chemical vapor deposition (VLPCVD). The crystal structure and epitaxial nature of the Si1−xGex, layers were studied by X-Ray diffraction. The value of full width at half maximum (FWHM) was found to be 0.34° for the as grown Si1−xGex (400) peak. The metal-Si1−xGex/Si Schottky diodes were formed by depositing Pd on Si1−xGex/Si at room temperature (RT=300K) and low temperature (LT=77K). The Schottky barrier heights and current transport mechanisms were determined by current-voltage-temperature (I-V-T) measurements. The interface property of Pd/ Si1−xGex/Si were studied as a function of metal deposition and post annealing temperatures.

We present here low temperature transport properties of Ru2Si3 single crystals. Below room temperature the resistivity behaviour of this material is extrinsic. The Hall coefficient is positive down to about 10 K and the becomes negative below. We explain this crossover with a two band model. At very low T, the magnetoresistance of our crystals shows the typical behaviour for a doped semiconductor on the metallic side of the metal-insulator transition and can be described by a scaling law characteristic for weak localisation with strong electronelectron interactions.

PtSi thin films prepared by UHV sputter-deposition procedures on n-type Si(100) wafers have been studied with the following techniques: (a) X-ray absorption fine structure spectroscopy at the Si K-edge, Si L2,3-edge, and Pt L3-edge; (b) X-ray reflectivity at photon energies below and above the Pt L3-edge threshold and (c) Photoemission. These techniques provide valuable information about the electronic structure, morphology, local structure, thickness, density and roughness, and surface and interface properties of the films. Preliminary results from the application of these techniques to the study of several PtSi thin films (with thickness from several hundreds to thousands of Å) are reported.

We investigated the formation of a buried HfSi2 layer by high fluence ion implantation of isotopically mass separated 179–180 Hf+ on heated silicon (100) substrates. It is shown that for the substrate temperature of 600°C a buried HfSi 2 layer is formed. By subsequent annealing at 1000 °C a continuous 12 nm HfSi2 layer on the Si surface is formed followed by 130 nm big almost spherodized HfSi2 ellipsoid and 80 nm small HfSi2 and Si grains. The annealing of samples implanted at lower temperatures show that HfSi2 is also formed but with reduced yield. A summary of the relevant data is presented.

The growth kinetics of the iridium silicides, IrSi and IrSi1.75 formed by RTA in vacuum has been characterized as a function of the processing temperature, up to 675°C, and annealing time for iridium films of different thickness. The sample temperature was measured using as a reference the SPE growth rate of amorphized silicon processed in the same RTA conditions. The samples were characterized by RBS, HREM, XRD and microdiffraction. RBS spectra show that the transition region between IrSi and IrSi1.75 is slightly gradual, while the interface between the IrSi and the iridium metal is sharp. The layer thickness of each silicide as a function of temperature and time was obtained from the RBS spectra. The activation energy of the diffusion coeficient of Si in IrSi and IrSi1.75 are about 1.3 eV and 3.9 eV respectively. Phase kinetics are the same for both thin and thick samples processed at the same temperature and annealing time when unreacted iridium remains in the film. However, the phase evolution is different when the annealing time is long enough to convert all the iridium metal into silicide in the thin film sample but not in the thick one. In this case, IrSil.75 is the only phase found if the annealing time is long enough. Silicides formed at 525°C consist mainly of polycrystalline IrSi, with grain size between 3 and 10 nm, and some isolated grains of IrSi 1.75. The interface between the IrSi and the Si is flat, very sharp, and well oriented grains grow from it. In order to avoid the IrSi1 75 formation and to obtain IrSi layers at reasonable rates, an RTA process at 500°C is proposed.

Concentrations of atmospheric impurities in tungsten silicide films and impurity areal densities silicide / polysilicon interface can usually only be measured using Secondary Ion Mass Spectrometry (SIMS). Normally these measurements are made using a Cs+ primary beam with negative secondary ions being monitored. This mode is used to achieve the best possible detection limits. However the Relative Sensitivity Factors (RSFs) used to quantify the impurities, as well as the reference matrix signal, change dramatically in going from one matrix to the other. These changes affect the quantification of the impurities at the interface. An alternate mode of analysis would be to use the Cs+ primary beam and monitor MCs+ ions, where M is the impurity, because these ions typically have less matrix dependent RSFs. We measure carbon and oxygen in a tungsten silicide film on polysilicon using both modes of analysis. Preliminary data indicates that we have determined the absolute accuracy of interface areal density to within a factor of 2.2 for oxygen and to within a factor of 1.5 for carbon.

Electroless metal deposition based upon the addition of fluoride anions to the metal salt aqueous solution have been developed recently on the assumption that the cleanness of the substrate will be guaranteed and the deposit will be of high purity. In this work, platinum is deposited on silicon (100) from fluorinated solution at two different pH's. The influence of pH is analyzed using Tapping Mode Atomic Force Microscopy (TMAFM) to characterize the main morphological properties of the deposit. Combined TMAFM and Transmission Electron Microscopy (TEM) images are presented and X-ray Photoelectron Spectroscopy (XPS) allows us to identify the chemical nature of the silicon surface.

TaSi2, and NbSi2 are superconductors below 353 mK and 130 mK respectively. These compounds, like VSi2 which is not superconducting down to 100 mK, crystallise in the C40 structure. They differ by a slight variation of lattice parameters.

We have systematically investigated the superconducting properties of several samples of TaSi2 by magnetic and resistive measurements. A small difference on Tc is observed for the same crystal by the two techniques. Several explanations are presented for this result.

We also report a change of Tc under pressure in good agreement with those resulting of the volume variation for the two C40 superconductors previously studied.

Tungsten / silicon multisandwich layers were deposited by DC magnetron sputtering on silicon and silicon oxide substrates. After the deposition the samples were annealed by rapid thermal annealing at different temperatures under H2 atmosphere. X-ray diffraction measurements were carried out to determine the crystal structure of the obtained silicide layers. To estimate the grain size and the relative lattice strain in dependence on the annealing temperature from the X-ray profile the deconvolution method of Lagrange was used. To characterize the electrical properties the specific resistance was measured by a linear four-point method. The best specific resistance measured was approximately 17 μΩcm for the sample on silicon substrate annealed at 1195 °C for 20 seconds. Rutherford Backscattering Spectroscopy measurements were carried out to obtain the stoichiometric depth profile.

Thin (CsCl)CoSi films of thicknesses from 44 to 105 Å were grown by MBE at room temperature onto ultrathin annealed CoSi2 templates. Also two CoSi2 films of about 100 Å with the CaF2 structure and with the defected CsCl structure were obtained epitaxially.

Far infrared reflectance and transmittance measured on such samples show optical structures between 240 and 370 cm-1. In the range 1.4–5 eV spectroscopic ellipsometry was performed, too. A change in the optical response was revealed among the different samples, which can be ascribed to strain, roughness and/or disorder at the interfaces.

Wsi2 films were prepared by rapid thermal annealing (RTA) in the temperature range of 800 -1400 °C for time durations of 15 sec -3 minutes. In some of the treatment experiments different gases were involved and a conclusion is made about the role of hydrogen favoring Wsi crystal phase growing at 800 °C. W films with thichnesses in the range 200 Å - 1000 Å were deposited on monocrystalline Si by pyrolitical decomposition of W(CO)6 in CVD reactor at atmospheric pressure and argon atmosphere. Reflection High Energy Electron Diffraction (RHEED) and Scanning Electron Microscopy (SEM) technics were used for structural characterization and FPP-100 device for resistance measurements. Results show that by solid state reaction applied at different RTA processes WSi2 phase could be formed.Resistivities as low as 2-3 mΩ.cm are obtained for 800 -1000 °C.