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ABSTRACT: The electromigration lifetime of dual-damascene Cu interconnects was found to significantly decrease with increasing linewidth, for linewidths ranging between 0.2 and 2.25 μm. Voids were also found to preexist in these lines. When void nucleation is required for failure, the electromigration reliability is generally found to be at most weakly dependent on the linewidth. In contrast, the current study suggests that growth, drift, and accumulation of existing voids lead to the observed strong linewidth dependence.
Applied Physics Letters 05/2007; 90(19):193505-193505-3. · 3.84 Impact Factor
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ABSTRACT: Electromigration has been characterized in via-terminated interconnect lines with additional vias in the middle, creating two adjacent segments that can be stressed independently. The mortality of a segment was found to depend on the direction and magnitude of the current in the adjacent segment, confirming that there is not a fixed value of the product of the current density and segment length, jL , that defines immortality in individual segments that are part of a multisegment interconnect tree. Instead, it is found that the probability of failure of a multisegment tree increases with the increasing value of an effective jL product defined in earlier work. However, contrary to expectations, the failures were still observed when (jL)<sub> eff </sub> was less than the critical jL product for which lines were found to be immortal in single-segment test structures. It is argued that this is due to reservoir effects associated with unstressed segments or due to liner failure at the central via. Multisegment test structures are therefore shown to reveal more types of failure mechanisms and mortality conditions that are not found in tests with single-segment structures.
Journal of Applied Physics 06/2006; · 2.17 Impact Factor
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ABSTRACT: Failure mechanisms observed in electromigration (EM)-stressed dual damascene Cu/SiO<sub>2</sub> interconnect trees were studied by stressing at fixed conditions for a short time followed by stressing with increasing current to induce Joule heating. Similar failure sites as those observed in samples stressed at normal EM conditions were found. This suggests that Joule heating can be used to accelerate some EM failure mechanisms that occur in normal EM experiments. Finite element method (FEM) simulation showed that the failure mechanisms could be due to Joule heating of Ta diffusion barrier after fully-spanning void was formed. The probabilistic existence of the post-stress 'volcano craters' and melt patches is highly dependent on the void growth mechanism during EM stressing.
Physical and Failure Analysis of Integrated Circuits, 2003. IPFA 2003. Proceedings of the 10th International Symposium on the; 08/2003
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ABSTRACT: The reliability of Cu dual-damascene interconnect trees with 3-terminal (dotted-I), 4-terminal (‘T’) and 5-terminal (‘+’) configurations has been investigated. The lifetime of multiterminal interconnect trees with the same current density through the common middle via was determined to be independent of the number of segments connected at the common junction. Furthermore, our experimental results on dotted-I test structures showed an increase in the reliability of the interconnect tree when the distribution of a same current was not equal in the two connected segments, especially for the cases where one of the segments was acting as a passive reservoir or active source of Cu atoms for the adjoining segment. Due to the low barrier for void nucleation at the Cu/Si3N4 interface, the presence of any small atomic source in neighboring segments will enhance the reliability of a connected segment in which Cu atoms are being drained away. As a consequence, failure can occur in a tree segment which is stressed at significantly lower current densities than more highly stressed adjoining segments.
MRS Proceedings. 12/2002; 766.
