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The formation of titanium disilicide (TiSi2) from Ti deposited using ionized metal plasma under different deposition conditions has been investigated. It is shown that deposition at elevated substrate temperature (450°C) enhances the formation of the low-resistivity C54 TiSi2, especially in patterned narrow lines. Grain-boundary footprint pictures obtained by atomic force microscopy indicate a larger grain-size distribution for the films deposited at higher substrate temperature. Deposition under substrate bias resulted in reduced contact resistivity. However, the use of substrate bias results in increased probability of bridging of silicide over the isolating spacers.

TiSi 2 was formed on amorphous, polycrystalline or single crystal silicon. Undoped samples are compared with specimens where the silicon had been doped with phosphorus or arsenic prior to titanium deposition. A non-destructive optical technique, total intergrated scattering (TIS) was used together with more conventional methods to evaluate the surface conditions after various treatments. These analyses were correlated with Rutherford backscattering spectrometry (RBS) to obtain more comprehensive information on the bulk morphologies. The dopant species play an important role for the morphology and stability of these structures. It is shown that TiSi 2 on undoped polysilicon is unstable at temperatures above 800°C and that an amorphous substrate offers potential advantages such as a smoother and more stable silicide.

The morphological instability of bilayers of NiSi, or CoSi 2 , on polysilicon has been investigated as a function of the thickness of the silicide, the presence of alloying additions and the initial oxidation of the silicide layer. The effect of Ir additions in enhancing the stability of the bilayers and the formation of NiSi 2 confirms the expectation that the morphological instabilities and the nucleation of NiSi 2 are dictated by surface energy effects (capillarity). Stresses may play a role in the initial step of the process which ultimately leads to a nearly complete inversion of the positions of the silicide and polysilicon layers. However, it is quite certain that the main driving force is the change in grain boundary energy of the polysilicon which starts with very small grains to begin with and ends up, at a different location, with much bigger grains.

The phase formation during rapid thermal annealing of a Ti/Mo bilayer sequentially deposited on Si substrates has been studied. The Mo layer varied from 0.5 to 2 nm and the Ti layer was always 60 nm thick. The presence of the Mo interposing layer enhances the formation of the C54 of TiSi2 by first forming a Mo‐bearing silicide phase of hexagonal structure. The desired C54 phase then nucleates and grows on top of this Mo‐bearing silicide phase at a temperature as low as 650 °C via Si diffusion through the growing silicide layers. This is about 100 °C lower than what is usually needed for the C49–C54 transformation. The significance of this finding is that the usual route for the formation of TiSi2, i.e., the C49 phase forms as a result of the Ti–Si interaction and the C54 phase forms as the product of phase transformation, is altered by the interposition of a thin refractory metal (here Mo) layer between Ti and Si.

NESTOR is a submarine high-energy muon and neutrino telescope, now under construction for deployment in the Mediterranean close to Greek shores. The first floor of NESTOR with 12 optical modules was deployed successfully in March 2003 together with the electronics system. All systems and the associated environmental monitoring units are operating properly and data are being recorded. The status of the NESTOR project is presented. We outline briefly the construction of the deepwater neutrino telescope, properties of the NESTOR site, infrastructure of the project, the deployment of the first floor, and its current operation. The first data are presented and plans for the next steps are summarized. © 2004 MAIK "Nauka/Interperiodica".

A previous investigation revealed that during annealing at high temperatures a CoSi 2 /polysilicon bilayer breaks down, resulting in an inverted bilayer structure because of silicon grain growth and cobalt redistribution. The present paper is devoted to the electrical effects of the observed phenomena. MOS capacitors were subjected to heat treatments in the range 750–900°C prior to the evaluation of breakdown statistics. The electrical results were compared with Rutherford backscattering spectrometry. It is concluded that the effects on gate oxide integrity are slight and reproducible even after partial inversion of the bilayer structure.

In the synthesis of combinatorial chemical libraries on solid phase, there is a need to cleave the compounds from the solid support before the library can be tested for biological activity. It is advantageous to use linkers which will release the libraries by mild photolytic cleavage. We have developed six new linkers of the photosensitive alpha-methyl 2-nitrobenzyl type containing amino, hydroxy, bromo and methylamino groups, and also 4-nitrophenoxycarbonyl activated OH and NH2 groups.

Using nondestructive pressure contacts, a GaAlAs double heterostructure (DH) wafer may be operated as a solar cell. When the spectrum of the photocurrent is observed, the band edge of the active layer is clearly identifiable. A model of photocurrent in a GaAlAs DH wafer shows that a reliable measurement of the active layer band edge can be made in spite of substantial variations in spectral shape that can be caused by variations in the GaAs cap layer thickness. Using this method, the emission wavelength of a laser can be predicted to ±62 A with 90 percent confidence, making photocurrent spectroscopy a useful tool for characterizing wafers.

The technique of programming the carrier gas flow rate in gas chromatography, especially in connection with the use of capillary columns shorter than 10 m can significantly accelerate GC analyses. Equations for calculation of the parameters of the exponential flow function and retention data are described. The effects of flow programming in a short capillary column are shown in a few chromatograms. Different programming rates are tested and compared with temperature programming.

An aluminium-silicon alloy has been adopted as the top metal layer over a Ti/TiN contact to silicon. The integrity of shallow contacts, after annealing at various temperatures, is investigated and compared with that obtained with pure aluminium over the nitride barrier. It is demonstrated that the incorporation of silicon (1%) in the aluminium metallization does not improve the stability of this system. Excessive leakage currents are observed in diodes annealed at temperatures above 500°C. The degradation is coupled to and aggravated by the presence of titanium. Electrical evaluation of the contact structures include diode leakage and contact resistance measurements. Some samples were examined by SEM after the metallization had been removed. The present knowledge of the thermodynamics of the systems involved is taken into consideration for the interpretation of the results.

Dual work function gate electrodes have been implemented in a 1- mu m CMOS process. Dopant atoms were implanted into tungsten silicide simultaneously with the source-drain implantations and subsequently diffused into the underlying polycrystalline silicon layer by rapid thermal annealing. Physical analyses showed that arsenic and boron could easily be incorporated in the polysilicon to concentrations greater than 10/sup 20/ cm/sup -3/. Capacitor and transistor measurements confirmed that n/sup +/ and p/sup +/ silicon could be obtained, with a difference of about 1 V between the respective flat-band voltages. By comparison with conventional n-type gate MOSFETs, it was verified that significantly improved subthreshold characteristics were obtained with p-type PMOS gate electrodes. >

The influence of high temperature processing steps on the integrity of a polycide metal-oxide-semiconductor system has been investigated. At temperatures exceeding 900°C the TiSi 2 /poly-Si (where poly-Si is polycrystalline silicon) system is not stable, and the dielectric strength of an underlaying gate oxide deteriorates. Degradation of the silicide-poly-Si interface was detected by backscattering spectrometry. Scanning and transmission electron microscopy revealed silicon precipitation and silicide film deformation.

The usefulness of Ti/TiN and TiSi 2 /TiN bilayers as low resistive contacts and diffusion barriers between doped silicon and aluminium has been examined. The Ti layer was magnetron sputtered and the TiN layers were deposited by reactive magnetron sputtering in an argon/nitrogen mixture. After Ti/TiN deposition part of the samples were annealed in a vacuum furnace to form a TiSi 2 /TiN structure. The films were characterized by Rutherford backscattering spectrometry (RBS), X-ray diffractometry (XRD) and resistivity measurements. The integrity of the final metallization systems, with aluminium as top level, for annealing temperatures in the range 400–600°C was evaluated by RBS and electrical measurements on fully processed test vehicles containing structures for contact resistivity measurements and shallow implanted gated diodes. A significant discrepancy has been observed between recorded RBS data and electrical measurements. No reaction was detected by RBS at temperatures below 525°C although a significant degradation of the electrical performance was readily observed at lower annealing temperatures, e.g. an increase in contact resistance and large reverse leakage currents. It is concluded that RBS, commonly used in the study of diffusion barrier properties, gives optimistic information on the upper limit of the metallurgical stability of the barrier layers, whereas other factors such as step coverage, compositional variation and mechanical stress are of predominant significance when actual device metallization is concerned.

An intermittent loss of light output in AlGaAs lasers modulated at 90 Mbit/s is investigated and is attributed to a parallel intermittent shunt that switches between a resistive and conducting state. The shunt is associated with the presence of In contamination on the sidewalls of the laser chip. A calculation of the switching time based on conducting filaments through In 1-x O x is consistent with the pulsed operation of the laser in testing. This shunt is avoided if bonding techniques that eliminate In from sides of the laser chips are employed.

1. Isolated cells from disintegrated monosiphonous branches of the rhodophyceanDasya pedicellata are able to grow into fully developed plants and to perform vegetative propagation. 2. Cultures of germlings from those cells, as well as carpospores and tetraspores, attain maximum growth rates in salinities lower than that of normal sea water. 3. In spite of its sublittoral occurrence,Dasya pedicellata tolerates a wide range of salinities.

1. Le thalle adulte duStriaria attenuata ne porte que des zoidocystes uniloculaires. Sa presence est reguliere en France, mais plus irreguliere en Suede. 2. Des cultures comparees, faites dans les deux pays, ont montre des variations dans le cycle de l'algue. 3. En France, le cycle, sexue, est double: (a) digenetique, heteromorphe, diplohaplophasique (2n=20 et n=10 chromosomes environ); (b) monogenetique, diplophasique, par la copulation immediate des zoides des zoidocystes uniloculaires. 4. En Suede, le cycle, asexue, est sans doute entierement diplophasique, la germination directe des zoides donnant une succession de microthalles porteurs, soit de zoidocystes uni- et pluriloculaires seulement, soit de zoidocystes pluriloculaires et deStriaria adultes.

An evaluation of the processing of zirconium nitride and the usefulness of this nitride as a diffusion barrier between aluminum and silicon has been carried out. Reactive sputtering from an elemental zirconium target in a mixture of Ar/N2 makes it possible to change the nitrogen content in the deposited film. The composition variation with N2 concentration will be presented. Films have been prepared using rf‐diode reactive sputtering. The as‐deposited film resistivity dependence on bias voltage has also been studied. Zirconium deposited on silicon forms a silicide at 550–600 °C. We have found by Rutherford backscattering spectroscopy analysis that during this silicide formation on arsenic implanted silicon substrates, the arsenic is piled up at the silicon/silicide interface. This effect favors the formation of a low resistance Ohmic contact. Since the barrier height between the silicide and silicon is expected to be 0.55 eV we want to point out that this contact may be useful for both n‐ and p‐type regio...