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  • 1
    Electronic Resource
    Electronic Resource
    Slit morphology of electromigration induced open circuit failures in fine line conductors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3201-3203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed transmission and scanning electron microscopic images of electromigration-induced open circuit failures are presented for fine line aluminum alloy thin film interconnects. A characteristic slit open circuit, similar to stress migration open circuits in narrow interconnects, is shown for various film compositions, processing, and deposition conditions. It is suggested that slit failure morphology is more generally observed for low (≈1) ratios of conductor line width to film grain size. The slit failures observed often occur near copper rich precipitates. The morphology of several slit voids suggests that they are transgranular across the linewidth, consistent with other recent reports of electromigration induced damage in single crystal interconnects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351484
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  • 2
    Electronic Resource
    Electronic Resource
    The mechanism of electromigration failure of narrow Al-2Cu-1Si thin-film interconnects (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4885-4893 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work is principally concerned with the microstructure of electromigration failure in narrow Al-2Cu-1Si conducting lines on Si. Samples were patterned from 0.5-μm-thick vapor-deposited films with mean grain size of 2.4 μm, and had linewidths of 1.3 μm (W/G≈0.5), 2 μm (W/G≈0.8), and 6 μm (W/G≈2.5). The lines were tested to failure at T=226 °C and j=2.5×106 A/cm2. Other samples were tested over a range of substrate temperatures and current densities to test the effect of these variables, and 1.3 μm lines were tested after preaging at 226 °C for various times to change the Cu-precipitate distribution prior to testing. Three failure modes were observed: The 6 μm specimens failed by separation along grain boundaries with an apparent activation energy of 0.65 eV; the 1.3 μm specimens that were preaged for 24 h failed after very long times by gradual thinning to rupture; all other narrow lines failed by the transgranular-slit mechanism with an activation energy near 0.93 eV. Microstructural studies suggest that the transgranular-slit failure mechanism is due to the accumulation of a supersaturation of vacancies in the bamboo grains that terminate polygranular segments in the line. Failure occurs after Cu has been swept from the grain that fails. Failure happens first at the end of the longest polygranular segment of the line, at a time that decreases exponentially with the polygranular segment length. Preaging the line to create a more stable distribution of Cu lengthens the time required to sweep Cu from the longest polygranular segment, and significantly increases the time to failure. In the optimal case the transgranular-slit failure mechanism is suppressed, and the bamboo grain fails by diffuse thinning to rupture. Preaging is particularly effective in increasing the lifetimes of lines that contain very long polygranular segments, and has the consequence that the time to first failure in an array of lines is much longer than predicted by a log-normal fit to the distribution of failure times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353806
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of Cu precipitation on electromigration failure in Al-Cu-Si (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1837-1845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper reports a study of the effect of Cu precipitation on electromigration failure in Al-2Cu-1Si thin-film conducting lines. The films were 0.5 μm in thickness, and patterned to widths of 1.3 and 4 μm, providing width-to-grain-size ratios (W/G) of approximately 0.5 and 2. The lines were aged for various times at 226 °C, and were then tested to failure at a current density of 2.5×106 A/cm2. Scanning and transmission electron microscopy were used to study the Cu precipitate distribution, its evolution during aging and electromigration, and the microstructural failure mechanism. Aging produces a dense distribution of intragranular θ' (Al2Cu; coherent), with stable θ (Al2Cu; incoherent) in the grain boundaries. The θ' is replaced by θ as aging proceeds. In the wide lines (W/G≈2), the mean time to failure (MTF) increases slowly and monotonically with prior aging time. The failure happens through the growth and coalescence of intergranular voids. In the narrow lines (W/G≈0.5), both the MTF and the time to first failure increase by more than an order of magnitude when the line is aged for 24 h prior to testing, then decrease on further aging. The dominant failure mode is the "slit'' failure mode previously observed in pure Al. However, the 24 h specimens fail by gradual, uniform thinning. Failure occurs in regions that have been swept free of intragranular precipitates. The failure time appears to be proportional to the intragranular density of θ precipitates, and related to the time required to sweep these from a critical length of line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351655
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  • 4
    Electronic Resource
    Electronic Resource
    Observation of magnetic gradients in stainless steel with a high-Tc superconducting quantum interference device microscope (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1977-1982 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting quantum interference device (SQUID) microscopes may serve as useful nondestructive evaluation (NDE) tools since they can precisely measure the local magnetic field variation that can be related to the characteristics of ferromagnetic materials. To demonstrate this, we have studied magnetic functionally graded materials (FGMs) in the Fe–Cr–Ni alloy system using a high-transition-temperature (HTc) SQUID microscope. The FGMs were either fabricated by inhomogeneous mechanical deformation or by heat treatment in a temperature gradient. The magnetic properties of these materials were measured using the vibrating sample magnetometer technique along the deformation or the temperature gradients. The results from this technique and the microstructural properties from optical imaging are discussed in conjunction with the magnetic field images obtained from the SQUID microscope. By exploring the results, the feasibility and benefit of utilizing SQUID microscopy as a NDE tool are discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1334637
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of microstructure on the resistivity of Al-Cu-Si thin-film interconnects (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 879-884 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The rate of resistivity decay in Al-2Cu-1Si thin-film conductors was studied as a function of temperature and grain size distribution. The decay kinetics were assumed to be governed by the rate of precipitate reconfiguration to grain boundaries. This assumption was confirmed by transmission electron microscopy (TEM) observations of the microstructure during resistance decay, and by studies of lines of two different widths. The results can be explained qualitatively from the microstructure of the lines. In particular, increasing the mean grain size slows the rate of resistivity decay, and establishing a bimodal distribution with a significant population of relatively large grains has the same effect. A simple model was developed to treat these effects quantitatively. The model assumes a cylindrical grain geometry and a uniform initial distribution of Cu and ignores the effect of intragranular precipitation. The model yields reasonable values for the activation energy for Cu diffusion in thin films, and predicts the correct dependence of the decay rate on grain size and grain distribution; however, it appears to overestimate the value of the preexponential factor D0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356442
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of post-pattern annealing on the grain structure and reliability of Al-based interconnects (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8330-8335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The possibility is addressed of improving the electromigration resistance of Al and Al–Cu thin-film conductors with "quasi-bamboo'' structures by post-pattern anneals that decrease the maximum polygranular segment length. Pure Al, Al–2Cu, and Al–2Cu–1Si lines were patterned and annealed at temperatures high enough to stimulate grain growth. Appropriate anneals led to predominantly bamboo structures with short polygranular segments. These grain structures had a high median time to failure with a relatively low deviation of the time to failure. Metallographic analyses showed that polygranular segment length was a dominant factor in determining the failure site. Post-pattern annealing promotes a preferential shortening of the relatively long polygranular segments that cause early failures. However, even after annealing, failure occurred at the longest residual polygranular segments, even when these were significantly shorter than the "Blech length'' under the test conditions. Statistical analysis of the failure of alloy lines revealed a simple exponential relation between the failure time and the longest polygranular segment length within a line, which is functionally identical to that previously found for lines tested in the as-patterned condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362545
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of electromigration-induced edge drift in Al–Cu thin-film interconnects (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1592-1598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article employs a one-dimensional diffusion model to study the phenomenon of electromigration-induced edge drift in a finite, Al–Cu thin-film conductor. Edge drift is caused by the accumulation of vacancies at the negative (upstream) terminal of the conductor as Al diffuses with the electrical current. When the Cu content exceeds its solubility limit, grain boundaries are decorated with Al2Cu precipitates, which must be dissolved before significant Al diffusion occurs. Assuming one-dimensional flow in a homogeneous, polygranular film, we compute the rate of growth of the precipitate-free zone at the upstream terminal, and estimate the incubation time for the onset of edge drift. The results predict an incubation time that increases with the grain size and the initial Cu content, and decreases with the square of the current density. The incubation time is inversely proportional to the "electromigration diffusivity", DE=DBCuδZCu*, the product of the grain boundary diffusivity of Cu, the effective grain boundary thickness, and the effective valence of the Cu ion. The results are used to compare a number of prior experimental studies, which are shown (with one exception) to produce consistent values for DE. An analysis of the experimental results suggests that edge drift begins almost as soon as the precipitate-free zone length exceeds the "Blech length" for the line, suggesting that the presence of Al2Cu precipitates in the grain boundaries is essential to retard Al electromigration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365948
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  • 8
    Electronic Resource
    Electronic Resource
    Intensities of backscatter Mössbauer spectra (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2550-2555 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intensities of γ-ray and x-ray backscatter Mössbauer spectra of 57Fe nuclei in different matrix materials were studied theoretically and experimentally. A previous analysis by J. J. Bara [Phys. Status Solidi A 58, 349 (1980] showed that negative peak intensities occur in backscatter γ-ray spectra when the 57Fe nuclei are in a matrix of light elements. We report a confirmation of this work and offer a simple explanation of the phenomenon. The present paper extends Bara's analysis to the case of conversion x-ray spectra; expressions for the intensity of conversion x-ray spectra as a function of absorber thickness and absorber material parameters are presented. We show that negative peak intensities are expected in conversion x-ray spectra when the 57Fe nuclei are in a matrix of heavy elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341641
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  • 9
    Electronic Resource
    Electronic Resource
    Sequence of phase formation in Nb/Al multilayered samples (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3487-3491 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of Nb/Al multilayered samples made by a sputter-deposition or a cold-rolling technique was used to simulate reactions in powder metallurgy processed Nb/Al superconducting wires. The sequence of phase formation observed in the Nb/Al multilayered samples was explained using knowledge about the crystal structure of each compound. Three different controlling mechanisms were proposed: the activation energy for nucleation, the energy barrier associated with short range order, and the diffusion barrier by the previously formed phase layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341484
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  • 10
    Electronic Resource
    Electronic Resource
    Quantitative in situ nanoindentation in an electron microscope (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1625-1627 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the development of a method for quantitative, in situ nanoindentation in an electron microscope and its application to study the onset of deformation during the nanoindentation of aluminum films. The force–displacement curve developed shows the characteristic "staircase" instability at the onset of plastic deformation. This instability corresponds to the first appearance of dislocations in a previously defect-free grain. Plastic deformation proceeds through the formation and propagation of prismatic loops punched into the material, and half loops that emanate from the sample surface. These results represent the first real time observations of the discrete microstructural events that occur during nanoindentation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1400768
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