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The influence of microstructure on the probability of early failure in aluminum-based interconnects

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journal contribution
posted on 2009-07-14, 11:18 authored by Vincent Dwyer
For electromigration in short aluminum interconnects terminated by tungsten vias, the well known “short-line” effect applies. In a similar manner, for longer lines, early failure is determined by a critical value Lcrit for the length of polygranular clusters. Any cluster shorter than Lcrit is “immortal” on the time scale of early failure where the figure of merit is not the standard t50 value (the time to 50% failures), but rather the total probability of early failure, Pcf. Pcf is a complex function of current density, linewidth, line length, and material properties (the median grain size d50 and grain size shape factor σd). It is calculated here using a model based around the theory of runs, which has proved itself to be a useful tool for assessing the probability of extreme events. Our analysis shows that Pcf is strongly dependent on σd, and a change in σd from 0.27 to 0.5 can cause an order of magnitude increase in Pcf under typical test conditions. This has implications for the web-based two-dimensional grain-growth simulator MIT/EmSim, which generates grain patterns with σd =0.27, while typical as-patterned structures are better represented by a σd in the range 0.4 – 0.6. The simulator will consequently overestimate interconnect reliability due to this particular electromigration failure mode.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Citation

DWYER, V.M., 2004. The influence of microstructure on the probability of early failure in aluminum-based interconnects. The Journal of Applied Physics, 96 (5), pp. 2914-2922

Publisher

© American Institute of Physics

Version

  • VoR (Version of Record)

Publication date

2004

Notes

This article was published in the serial, Journal of Applied Physics [© American Institute of Physics]. It is also available at: http://dx.doi.org/10.1063/1.1771825

ISSN

0021-8979

Language

  • en

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