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  • 1995-1999  (9)
  • 1990-1994  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of silicide formation measured by in situ ramped resistance measurements (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4087-4095 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of "Kissinger'' plots to analyze in situ resistance monitoring of thin-film reactions during heating at a constant rate is widely accepted. One obtains the activation energy for diffusion, at least in the case of diffusion-controlled reactions. The aim of this article is to extend the analysis one step further and show that, provided that the thickness of the layers formed is known, the same experimental and analytical techniques may yield the pre-exponential growth factor. The validity of the procedure is demonstrated by comparing the results thus obtained with data from the literature derived by conventional analysis of compound growth during isothermal annealing. Such comparisons have been made for Co2Si, CoSi, CoSi2, Pt2Si, PtSi, Ni2Si, and NiSi formation on undoped polycrystalline Si and single-crystal Si on sapphire substrates with ramp rates ranging from 10−2 °C/s to 102 °C/s. Measurements used both conventional furnace and rapid thermal annealing. In the past, the common practice has been to use the Kissinger method regardless of the sequence of growing phases. However, for phases other than the first one to be formed the direct Kissinger analysis needs to be modified. In the present cases the results obtained by means of an appropriately corrected procedure are not significantly different; that may not always be true. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361771
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  • 2
    Electronic Resource
    Electronic Resource
    Polytype formation in zirconium-silicon thin films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 241-246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of zirconium silicide (ZrSi2, orthorhombic C49; a=0.369 nm, b=1.47 nm, c=0.366 nm) thin films has been investigated by high-resolution electron microscopy. The crystals are heavily faulted in the 010 plane with an average distance between faults of 1.6 nm. The fault has been found to be a π/2-rotation twin around the b axis, the habit plane lying between two silicon layers. The crystals contain an equal number of 〈a〉- and 〈c〉-oriented slabs, giving rise to a strained lattice with an average a=c lattice parameter. On the basis of an elastic calculation, the fault energy is evaluated to be of the order of 5 ergs cm−2. This low energy explains the tendency to form polytypes which are mostly disordered, although some ordered sequences are favored at short range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345295
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  • 3
    Electronic Resource
    Electronic Resource
    Stability of C49 and C54 phases of TiSi2 under ion bombardment (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2660-2666 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transformation of C49 phase TiSi2 to the low resistivity C54 phase is necessary for many microelectronic applications. Here, we report on attempts to decrease this transformation temperature by low-energy ion bombardment at elevated temperature. Ion irradiation was performed using a broad beam Kaufman ion source operated in N2 or Ar gas between 0.1 and 2 keV beam energy, with ion doses ranging from 2.0×1016 to 1.9×1018 ions/cm2, and sample temperatures from 480 °C to 735 °C. For comparison, room-temperature Ar+ implantation at higher energy (105–210 keV) was performed with a dose of 1016 ions/cm2 with projected ranges within and beyond the TiSi2 layer thickness. Resistivity measurements as a function of temperature, x-ray diffraction, and Rutherford backscattering spectrometry were used to determine the composition and phases. Results show that low-energy ion bombardment does not promote the C49-C54 transformation at the temperatures studied, while ion implantation actually raises the temperature for the transformation. In addition, bombardment of C54 TiSi2 does not cause it to revert to the C49 phase, indicating that both phases appear to be surprisingly stable under ion bombardment. Simulations of defect production using the trim code indicate the formation of a higher number of displaced atoms than are usually required to initiate a transformation. We conclude that the defects introduced into C49 TiSi2 by ion bombardment at energies up to 2 keV are either not sufficient to nucleate the C54 phase or they are annealed out too quickly at the temperature needed for C54 phase growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349380
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  • 4
    Electronic Resource
    Electronic Resource
    Oxidation of titanium, manganese, iron, and niobium silicides: Marker experiments (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5133-5139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism of atomic transport inside the silicide during thermal oxidation of silicide layers on Si substrates has been analyzed by means of inert gas markers implanted in TiSi2, Mn11Si19, FeSi2, and NbSi2. Oxidation was carried out in dry oxygen. The marker displacement reveals that the growth of metal-free SiO2 over the first three of these compounds occurs via the reverse motion of metal atoms, from the silicide/oxide to the silicon/silicide interface, rather than through the direct diffusion of Si atoms from the substrate to the oxide. Moreover, analysis of the marker position indicates that the total amount of Si between the marker and the free surface decreases during oxidation, as had been previously observed in the oxidation of NiSi2, CoSi2, and CrSi2. Although this could occur via the formation and evaporation of SiO, it is believed that the loss of Si is due to the motion of Si atoms, also in the "reverse'' direction as for the metal atoms, across the silicide layer. The experiment conducted with NbSi2 shows that this silicide oxidizes via the direct motion of Si from the substrate to the oxide as anticipated. With TiSi2 the initial state of oxidation occurs as described, but the experimental observations imply that thick oxide layers grow via the direct motion of Si from the substrate to the oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347053
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  • 5
    Electronic Resource
    Electronic Resource
    Reduction of the C54–TiSi2 phase transformation temperature using refractory metal ion implantation (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3729-3731 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report that the ion implantation of a small dose of Mo into a silicon substrate before the deposition of a thin film of Ti lowers the temperature required to form the commercially important low resistivity C54–TiSi2 phase by 100–150 °C. A lesser improvement is obtained with W implantation. In addition, a sharp reduction in the dependence of C54 formation on the geometrical size of the silicided structure is observed. The enhancement in C54 formation observed with the ion implantation of Mo is not explained by ion mixing of the Ti/Si interface or implant-induced damage. Rather, it is attributed to an enhanced nucleation of C54–TiSi2 out of the precursor high resistance C49–TiSi2 phase. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115364
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  • 6
    Electronic Resource
    Electronic Resource
    Diffusion versus oxidation rates in silicon-germanium alloys (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 78-80 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the oxidation of SiGe alloys of different compositions (between 25 and 75 at.% Ge). All of the oxidations were performed at 900 °C in wet atmosphere on 7500-A(ring)-thick films grown by molecular beam epitaxy. Below 50 at.% Ge, the oxidation remains similar to what has been described previously, i.e., initially, the rate is enhanced by the presence of Ge, the oxide formed is pure SiO2 and a Ge pileup forms at the SiO2/Si-Ge interface. In these relatively thick films, we propose that after extended oxidation, the decrease of Si concentration at the interface slows down oxidation rates enough so that eventually, the oxide thickness for the SiGe alloys ends up smaller than that of pure Si. For alloys containing above 50 at.% Ge, a markedly different behavior is found: A two-layer oxide is formed, consisting of a mixed (Si,Ge) O2 layer near the surface, and a pure SiO2 layer underneath. The rates of oxidation in this case are even faster, since both Ge and Si are being oxidized. The general behavior is explained in terms of the balance of Si and Ge diffusion fluxes, to and from the interface, needed to sustain oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105528
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  • 7
    Electronic Resource
    Electronic Resource
    The dominant diffusing species and initial phase formation in Al-Cu, Mg-Cu, and Mg-Ni systems (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4036-4040 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dominant diffusion species in the formation of Al2Cu, Mg2Cu, and Mg2Ni have been determined. These compounds, rich in the lower melting point elements, are the first phases formed in metal/metal binary reactions. It is quite surprising to find that in all three systems, the minority elements, i.e., Cu or Ni, are the dominant diffusing species. This is in marked difference with results obtained in many metal/metal and metal/Si systems, where the dominant diffusion species are usually the majority elements in the initially formed compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352258
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  • 8
    Electronic Resource
    Electronic Resource
    Removal of the process-induced fluorine associated to chemical vapor deposition of tungsten onto a polycrystalline silicon gate structure by heat treatment in a hydrogen-containing atmosphere (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2112-2120 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tungsten was deposited from a gas mixture of hydrogen and tungsten hexafluoride onto a polycrystalline silicon gate structure in a chemical vapor deposition system. During the deposition process fluorine was also deposited as an undesired impurity. In order to remove the fluorine, heat treatments in the temperature range 550–1050 °C were performed in a hydrogen atmosphere. By this treatment it is possible to form volatile hydrofluoric acid and hence remove fluorine from the structure. Nuclear-resonance-broadening technique and secondary ion mass spectrometry were used for the analysis of fluorine. Fluorine was detected in all the samples except for the sample heat treated at 1050 °C. Moreover, etching of the polycrystalline silicon was observed. The gettering of fluorine, the etching of silicon and the observed formation of tungsten disilicide at 650 °C are discussed with respect to conceivable mechanisms. A thermodynamic study supporting the interpretations is also included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346566
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  • 9
    Electronic Resource
    Electronic Resource
    Oxidation and formation mechanisms in disilicides: VSi2 and CrSi2, inert marker experiments and interpretation (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6213-6223 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The process of atomic transport in the silicide during oxidation of silicide layers formed on Si substrates has been analyzed by means of implanted inert markers. The results confirm that CrSi2 oxidizes via the diffusion of Cr atoms towards the Si substrate, and reveal that the same type of transport occurs in VSi2, which is in opposition to the growth of these disilicides that proceeds via Si motion. Moreover during the oxidation of both VSi2 and CrSi2, the diffusing metal atoms are accompanied by a large proportion of the Si atoms from the silicide which also diffuse towards the substrate. Thus, the experimental evidence now available reveals that all the silicon-rich silicides, in increasing atomic numbers from TiSi2 to NiSi2, oxidize with the formation of metal-free SiO2 in a process that involves the diffusion of both metal and Si regardless of the predominant moving species during silicide formation. In CrSi2, VSi2, as well as TiSi2, with similar structures, examination of the structure shows that diffusion should occur via a vacancy mechanism. The thermodynamic conditions that prevail during oxidation lead indifferently to metal diffusion in one direction or Si diffusion in the other. Any selection between one mechanism or the other has to be dictated by kinetic conditions relating to the relative mobilities of the two atomic species. What is known about this is discussed in detail. Finally it is proposed that the observed dual, parallel diffusion of metal and Si, results from the very nature of the oxidation process which modifies the chemical potential of the atoms at the surface being oxidized. Thus is created a force that drives some of the atoms away from the surface, into the inside of the samples. The best known example of this behavior is the often observed "injection'' of interstitials during Si oxidation, but a similar process is at work in silicide oxidation, with somewhat similar results. Volume effects, thought to play an important role in solid state chemical reactions, are remarkably well illustrated by the oxidation of silicides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346913
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  • 10
    Electronic Resource
    Electronic Resource
    In situ characterization of titanium silicide formation: The effect of Mo interlayer, temperature ramp-rate, and annealing atmosphere (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2617-2626 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of titanium silicides has been studied using simultaneous in situ x-ray diffraction with millisecond time resolution and sheet resistance measurements. The effect of a Mo interposed layer between Ti films and Si substrate was investigated by varying the thickness of the Mo interlayer from 0 (Ti/Si) to 1.8 nm (Ti/Mo/Si). The thickness of Ti was kept to 55 nm for all samples. Both isothermal annealing and ramp annealing in helium were performed in order to study the mechanism of silicide formation. While C49 TiSi2 was the only disilicide found after annealing Ti/Si at 650 °C for 20 min, C54 TiSi2 was readily formed in the presence of Mo. The formation of C49 TiSi2 was not observed with a 1.8 nm thick Mo interlayer. Instead, there was indication that C40 (Mo,Ti)Si2 was formed. In addition, broad diffraction peaks, weak in intensity, could be all assigned to Ti5Si4. However, the presence of Ti5Si4 alone did not induce the formation of C54 TiSi2. Even with a 20 °C increase in isothermal annealing temperature to 670 °C for 20 min, the presence of Mo was found to be a necessity for the formation of C54 TiSi2. When annealed in nitrogen, instead of helium, the formation of surface titanium nitride competes with the formation of silicides. The formation of C54 TiSi2 was even suppressed in the sample with a 1.8 nm Mo interlayer when annealed at 650 °C in nitrogen. The formation of Ti5Si4 and the role it plays in the formation of other silicides (C40, C49, and C54) are discussed on the basis of simple crystallographic considerations. The effect of a Mo interlayer and/or ramp-rate on the formation of C40 (Mo,Ti)Si2 and C49 TiSi2 is discussed in conjunction with variations of the preferential orientation of C54 TiSi2 films. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369626
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