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  • Articles: DFG German National Licenses  (17)
  • 1990-1994  (17)
  • 1994  (8)
  • 1992  (9)
Source
  • Articles: DFG German National Licenses  (17)
Material
Years
  • 1990-1994  (17)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Tantalum as a diffusion barrier between copper and silicon: Failure mechanism and effect of nitrogen additions (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5433-5444 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction of Cu with Si separated by thin (50 nm) layers of tantalum, Ta2N, and a nitrogen alloy of Ta has been investigated to determine the factors that affect the success of these materials as diffusion barriers to copper. Intermixing in these films was followed as a function of annealing temperature by in situ resistance measurements, Rutherford backscattering spectra, scanning electron microscopy, and cross-section transmission electron microscopy. Ta prevents Cu-silicon interaction up to 550 °C for 30 min in flowing purified He. At higher temperatures, copper penetration results in the formation of η‘-Cu3Si precipitates at the Ta-Si interface. Local defect sites appear on the surface of the sample in the early stages of this reaction. The Ta subsequently reacts with the substrate at 650 °C to form a planar hexagonal-TaSi2 layer. Ta silicide formation, which does not occur until 700 °C in a Ta-Si binary reaction couple, is accelerated by the presence of Cu. Nitrogen-alloyed Ta is a very similar diffusion barrier to Ta. It was found that Ta2N is a more effective barrier to copper penetration, preventing Cu reaction with the substrate for temperatures up to at least 650 °C for 30 min. In this case, local Cu-Si reaction occurs along with the formation of a uniform Ta5Si3 layer at the Ta2N-Si interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350566
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Temperature and substrate dependence of Ar sputtering of CoSi2 thin films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4527-4532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of 300 eV argon ion sputtering of CoSi2 thin films has been investigated in the range 50–600 °C. Compared with the low-temperature values, the high-temperature etch rate of CoSi2 on Si decreases by a factor of 3, while the sputtering yield ratio of Si to Co increases by a factor of 3.5. This leads to effective motion of the silicide layer into the Si substrate at temperatures above 400 °C. During sputtering of CoSi2 on SiO2, the thickness of the silicide layer decreases almost linearly with bombardment time until all the silicide is removed. Similar behavior is observed in low-temperature sputtering of CoSi2 on Si. However, at elevated temperatures (400 °C〈T≤600 °C), the etch rate of the silicide decreases significantly after an initial fast sputtering period. For CoSi2 on Si, experimental results show that while Si atoms are sputtered from the surface, Co atoms are released and diffuse to the silicide/Si interface where they react with the underlying Si substrate to form new CoSi2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351385
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetic analysis of C49-TiSi2 and C54-TiSi2 formation at rapid thermal annealing rates (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4978-4980 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352018
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The relationship between deposition conditions, the beta to alpha phase transformation, and stress relaxation in tantalum thin films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4918-4924 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352059
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of Al grain growth, Al2Cu precipitation, and dissolution in blanket thin films and fine lines (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2781-2790 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The apparent activation energy Ea for Al grain growth, Al2Cu (aitch-theta-phase) precipitation, and Al2Cu dissolution were determined by ramped resistance measurements for both Al(Cu) blanket films and patterned lines. The Ea's measured for the initial stages of grain growth in 0.5-, 1-, and 2-μm-thick Al(4 wt % Cu), Al(2 wt % Cu), and Al films ranged from 1.19 to 1.46 eV. The Ea's for grain growth were higher for 0.6–0.9-μm-wide Al(Cu) lines than for blanket Al(Cu) films 1.89–3.1 eV, and the temperature of the peak transformation rate occurred at a much higher temperature, 310–400 vs 90–155 °C. This is due to the geometric constraints in patterned lines. The Ea's for Al2Cu precipitation in Al(4 wt % Cu) and Al(2 wt % Cu) films varied from 0.86 to 1.25 eV. For 0.6-μm-wide Al(4 wt % Cu) lines, the Ea for Al2Cu precipitation was 1.7 eV. The Ea's for Al2Cu dissolution increased with decreasing Cu content from 1.62–1.74 eV to 2.23–2.30 eV with Al(4 wt % Cu) and Al(2 wt % Cu) films, respectively. The temperature of the peak reaction rate Tp for Al2Cu dissolution increased markedly with increasing film thickness at constant ramp rates. These results demonstrate that the microstructure and Cu distribution in Al(Cu) interconnections on microelectronic chips vary as a function of feature size. This implies that blanket film data is not necessarily applicable to patterned features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357543
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Intermetallic formation in copper/magnesium thin films—kinetics, nucleation and growth, and effect of interfacial oxygen (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5161-5170 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357231
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance in Co/Cu multilayers after annealing : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6601-6603 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayer films of [Co 10 A(ring)/Cu(t)]64 with copper thicknesses from t=10 to 29 A(ring) annealed for 1 h at temperatures about 350 °C showed a decrease in sample resistivity at 4.2 K. The giant magnetoresistance (GMR) maximums for as-deposited films at t=10 A(ring) and t=23 A(ring) shifted with annealing. The GMR decreased for t=10 A(ring) and t=23 A(ring) but increased for t=19 A(ring) and t=29 A(ring) indicating a complex behavior with annealing. Similarities with granular films are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358206
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  • 8
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance of dilute Cu(Co) granular films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6909-6911 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Granular films of Cu (Co) with Co concentrations from 5.4% to 12% in the as-deposited form had magnetization showing about 60% of the Co as ferromagnetic particles and exhibited giant magnetoresistance (MR) of about 20% at 4.2 K. Annealing at ∼310 °C increased the MR to 40% and also increased the saturation magnetization indicating additional Co precipitation. At higher annealing temperatures MR decreased to 1%. The Zhang theoretical model involving polarized conduction electron scattering at particle interfaces seems to give a reasonable description of our results including the quadratic behavior of MR vs [M(H)]2 and MR vs [Ms(T)]2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356777
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  • 9
    Electronic Resource
    Electronic Resource
    Crystallographic texture change during abnormal grain growth in Cu-Co thin films (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 177-179 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The addition of 0.4–8.6 at. % Co to Cu thin films strongly influences the temperature evolution of microstructure, stress, and resistivity. For concentrations near 1 at. % Co in coevaporated Cu-Co on oxidized Si, normal grain growth begins at about 75 °C, about 50 °C lower than in pure Cu. There is an abrupt decrease in resistivity and stress at a temperature which increases with Co content from 120 °C (0% Co) to 250 °C (8.6 at. % Co), and coincides with precipitation of Co within Cu grains. A dramatic change in texture is observed in both coevaporated and electroplated Cu-Co films upon annealing above 250 °C. As-deposited films have a three-component texture of (111) fiber, (200) fiber, and random but annealed films have a dominant (200) fiber texture. This "cube'' texture differs from the dominant (111) texture of annealed pure Cu, and appears to be coupled to an abnormal grain growth process since many grains are observed to be larger than ten times the film thickness. It is proposed that segregation of Co to external surfaces or to Cu grain boundaries may favor this (200) texture by selectively affecting grain-boundary mobility or the surface energy driven grain growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112664
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Highly selective sputtering of silicon from TiSi2 at elevated temperature (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1196-1198 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate almost 100% selective sputtering of silicon from TiSi2 using a combination of low energy ion bombardment and elevated temperature. TiSi2 was prepared by annealing 1000-A(ring)-thick Ti on (100)Si in He at 635 °C for 30 min to produce 2300-A(ring) thick TiSi2. Ion beam etching was carried out using 300 eV argon with a flux of 0.27 mA/cm2 at temperatures from 33 to 700 °C. In situ sheet resistance measurements were used to monitor the decrease in silicide thickness as a function of time. Near room temperature, ion etching causes normal sputtering of the silicide. However, at temperatures of 500–700 °C, the sheet resistance remains almost unchanged during ion beam etching. Analysis by Rutherford backscattering, with and without Xe markers, shows that Si atoms sputtered from the surface of these high-temperature samples are continuously replaced by Si diffusing from beneath the silicide layer. The thickness and composition of the silicide remain almost unchanged, but the dramatic change in sputtering behavior shows that the surface is enriched in Si. Compared with the room-temperature values, the absolute sputtering yield of Ti at 500–700 °C is decreased by a factor of 5, and the yield of Si is increased by a factor of 2. The net result is almost 100% selective sputtering of silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107403
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    Paper (German National Licenses)
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