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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3423-3430 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The crystallization of thin-film, amorphous Co-Si alloys has been studied in the composition range of 42–80 at. % Si. Structural relaxation of the amorphous alloys preceded the crystallization. Crystallization temperature decreased slowly with increasing Si concentration, but showed a sharp decrease near the stoichiometric silicide compositions of CoSi and CoSi2. The crystallization of alloys close in composition to the disilicide (Co0.33Si0.67 and Co0.29Si0.71) was a one-step process with an activation energy of about 1.3 eV and an Avrami exponent of 3. In situ kinetic studies revealed that for the stoichiometric Co0.33Si0.67 alloy, the Avrami exponent of 3 arose from three-dimensional crystal growth from nuclei whose density saturated at the early stages of the transformation. The heat release and the volume contraction during crystallization of the Co0.33Si0.67 alloy were measured to be 0.118 eV/atom and 0.6%, respectively. In the case of a Co0.2Si0.8 alloy, which is considerably richer in Si than the disilicide composition, complete crystallization was achieved in a two-step process with a higher activation energy of 2.1 eV for the primary crystallization.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2211-2218 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Solid-state interdiffusion reactions at Al/Ni interfaces in multilayer films have been studied using differential scanning calorimetry, cross-sectional transmission electron microscopy/microanalysis, and thin-film x-ray diffraction. Multilayer films with various modulation periods and an overall atomic concentration ratio of three Al to one Ni were prepared by alternate electron-beam evaporation in high- and ultrahigh-vacuum systems. We show calorimetric, microstructural, and compositional evidence that interdiffusion of Al and Ni leading to solid solutions precedes the formation of intermetallic crystalline compounds. Isothermal calorimetry indicates that Al3Ni subsequently nucleates in the interdiffused region at preferred sites. Calorimetric analyses also suggest that nucleation sites quickly saturate in the early stage of Al3Ni formation and that the nucleation site density strongly depends on the grain sizes of the deposited films. After coalescence into a continuous layer at the interface, Al3Ni thickens through a diffusion-limited process, in agreement with previous reports. A kinetic model is developed which yields calculated calorimetric traces in good agreement with experimental data. Our results suggest the importance of prenucleation interdiffusion, in addition to nucleation, in the selection of the first phase during thin-film reactions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate that depositing Ta diffusion barriers under ultra-high vacuum conditions without in situ oxygen dosing allows for variations both in microstructure and in the concentration of chemical impurities that severely degrade barrier performance. The effects of deposition pressure, in situ oxygen dosing at interfaces, hydrogen and oxygen contamination, and microstructure on diffusion barrier performance to Cu diffusion for electron-beam deposited Ta are presented. 20 nm of Ta diffusion barrier followed by a 150 nm Cu conductor were deposited under ultra-high vacuum (UHV, deposition pressure of 1×10−9 to 5 ×10−8 Torr) and high vacuum (HV, deposition pressure of 1×10−7 to 5×10−6 Torr) conditions onto 〈100〉 Si. In situ resistance furnace measurements, Auger compositional depth profiling, secondary ion mass spectrometry, and forward recoil detection along with scanning and transmission electron microscopy were used to determine the electrical, chemical, and structural changes that occurred in thin-film Ta diffusion barriers upon annealing. Undosed HV deposited Ta barriers failed from 560 to 630 °C, while undosed UHV barriers failed from 310 to 630 °C. For UHV Ta barriers, in situ oxygen dosing during deposition at the Cu/Ta interface increased the failure temperatures by 30–250 °C and decreased the range of failure temperatures to 570–630 °C. Undosed UHV Ta barriers have no systematic relationship between failure temperature and deposition pressure, although correlations between breakdown temperature, oxygen and hydrogen concentrations, and microstructural variations were measured.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3566-3568 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We show that when processing conditions closely mimic those used in the conventional self-aligned silicide process, the effective activation energy for the polymorphic phase transformation of orthorhombic base-centered (oC12) C49-TiSi2 to the low-resistivity orthorhombic face-centered (oF24) C54-TiSi2 phase is over 1 eV higher than previously reported literature values where a 1-step heat cycle was used. For C49-TiSi2 films formed at temperatures of 600 and 625 °C on (100) single crystal silicon substrates, the activation energy was determined to be 5.6±0.3 and 5.7±0.13 eV, respectively, for the transformation of this phase into C54-TiSi2 in the temperature range of 625–700 °C. The higher activation energy obtained with the simulation of the self-aligned silicide processing conditions suggests that the conventional processing may need to be modified for future semiconductor applications.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4978-4980 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have used in situ resistance versus temperature measurements to demonstrate that a 60 nm titanium thin film on polycrystalline silicon heated at rates up to 3000 °C/min always forms high-resistivity base-centered orthorhombic C49-TiSi2 before the low-resistivity face-centered orthorhombic C54-TiSi2 phase. Kinetic analysis of the shift in transformation temperatures with heating rate indicates that the activation energies for the formation of C49-TiSi2 and C54-TiSi2 are 2.1±0.2 and 3.8±0.5 eV, respectively, when formed during the same annealing cycle. The higher activation energy of formation of C54-TiSi2 as compared to C49-TiSi2 suggests that under very high heating rates and annealing temperatures, the formation of C49-TiSi2 before C54-TiSi2 might be completely or partially bypassed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4918-4924 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate that the high temperature polymorphic tantalum phase transition from the tetragonal beta phase to the cubic alpha phase causes a large decrease in the resistance of thin films and a complete stress relaxation in films that were intrinsically compressively stressed. 100 nm beta tantalum thin films with intrinsic stresses of 2.0×1010 dynes/cm2 (tensile) to −2.3×1010 dynes/cm2 (compressive) were deposited onto thermally oxidized (100) silicon wafers by evaporation or dc magnetron sputtering with argon. In situ stress and resistance at temperature were measured at 10 °C/min up to 850 °C in purified helium. Upon heating, the main stress mechanisms were elastic deformation at low temperature, plastic deformation at moderate temperatures and stress relief because of the beta-to-alpha phase transition at high temperatures. The temperature ranges over which the elastic and plastic deformation and the beta-to-alpha phase transition occurred varied with deposition pressure and substrate biasing. Incomplete compressive stress relaxation at high temperatures was observed if the film was initially deposited in the alpha phase or if the beta phase did not completely transform into alpha by 800 °C due to substrate biasing during the deposition. We conclude that the main stress relief mechanism for tantalum films with intrinsic compressive stresses to completely relax their stress is the beta-to-alpha phase transition, while for intrinsically tensile films, this transformation has a much smaller effect on the stress.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5156-5159 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Infrared (IR)-absorbance spectroscopy was investigated as a technique for monitoring titanium silicide formation during the reaction of Ti films on (100) Si substrates. Films annealed to various stages of reaction were monitored by x-ray diffraction, film resistivity, and optical reflectance in order to relate the changes in the IR-absorbance spectra to reaction progress. Films at different stages of reaction showed distinctly different extinction coefficients α, and absorbance versus wave-number curves. IR absorbance was determined to be a useful indicator of reaction progress, especially in those cases where samples at different stages of the silicidation reaction have the same resistance but different absorbance behaviors. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7874-7881 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In situ resistance versus temperature or time for reactions between 32 and 57.5 nm of titanium and undoped or doped polycrystalline silicon (boron, arsenic, or phosphorus, 7.9×1019–3.0×1020/cm3) has been measured and no clear correlation was found between the activation energy for the formation of the industrially important low-resistance C54-TiSi2 phase and its formation temperature. It is also demonstrated that with certain moderate doping levels typical of complementary metal-oxide-semiconductor manufacturing, boron or phosphorus-doped polycrystalline silicon can delay the formation of C54-TiSi2 more than arsenic-doped polycrystalline silicon. Finally, by using in situ resistance measurements, it is demonstrated that the "two-step'' thermal annealing process similar to a salicide process requires less thermal annealing time at high temperatures to form C54-TiSi2 than a single "one-step'' thermal anneal at the same temperature. © 1994 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 7040-7044 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We describe a simple quasi-in situ resistivity technique and its application to the study of C49 to C54 TiSi2 conversion in narrow (0.1-1.0 μm) lines. This technique allowed comparison of both aggregate conversion versus time at temperature behavior and individual-line conversion versus time behavior for silicide lines of different linewidths. As linewidth decreased, the aggregate conversion versus time at temperature behavior slowed, and the conversion behaviors of individual lines having the same linewidth became more variable. Both of these observations are consistent with a nucleation-site-density controlled reaction under conditions of low nucleation site density. Correlations were also found between individual line behaviors and resistance to agglomeration; resistance to agglomeration (for 0.35–1.0 μm lines already in the C54 phase) was highest for lines which had "prompt'' conversion behaviors (as measured by the sheet resistance drop during the first minute of the conversion anneal). Additional data concerning the sensitivity of the initial sheet resistances to formation anneal conditions and linewidth is also briefly discussed. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5161-5170 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In situ resistance measurements, x-ray diffraction, Rutherford backscattering spectrometry, transmission electron microscopy, isothermal and constant heating rate differential scanning calorimetry and Auger electron spectrometry depth profiles have been used to investigate the interactions in copper and magnesium thin films leading to the growth of Cu2Mg and CuMg2 intermetallics. The effect of exposing the reacting interfaces to controlled exposure of oxygen on the nucleation and growth kinetics of such intermetallics was also investigated. It is found that the first phase to form is CuMg2, at about 200–215 °C. It is determined that the formation of CuMg2 occurs by a two step process consisting of nucleation and growth. The nucleation of CuMg2 takes place in a region composed of a Cu/Mg solid solution. The nuclei form at certain preferred sites and grow in directions both parallel and perpendicular to the surface, eventually leading to a continuous CuMg2 layer. The growth of CuMg2 nuclei in the plane of the original interface occurs at a constant rate, whereas the growth in a direction perpendicular to the original interface is found to be diffusion limited. In the presence of excess copper Cu2Mg forms at higher temperatures, with complete conversion to Cu2Mg occurring at about 380 °C. When the Cu surface is dosed with oxygen prior to Mg deposition, ramp rate differential scanning calorimetry (DSC) shows that the nucleation and growth of CuMg2 as well as the growth of Cu2Mg are not disturbed. Dosing the Mg surface with oxygen results in significant changes in the growth of the two phases. In this case a thin MgO layer is formed at the oxygen dosed surface, lateral growth of CuMg2 is unaffected, but vertical growth of CuMg2 across the oxygen dosed interfaces is delayed by 25–30 °C. The growth of Cu2Mg is also shown to be delayed, by 22–54 °C due to the interfacial oxygen dose.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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