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Electromigration in Al/W and Al(Cu)/W Interconnect Structures

Published online by Cambridge University Press:  15 February 2011

C-K. Hu
Affiliation:
IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, NY 10598
P. S. Ho
Affiliation:
IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, NY 10598
M. B. Small
Affiliation:
IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, NY 10598
K. Kelleher
Affiliation:
IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, NY 10598
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Abstract

The electromigration drift velocity of Al in Al(3wt.% Si), Al(2wt.%Cu), and Al(2wt.%Cu,3wt.%Si) was measured in a temperature range 133 to 220 °C with current densities of 1.0 to 1.5×106A/cm2. In Al(3wt.% Si), a significant Al depletion at the cathode end and accumulation at the anode end of stripe were observed within a few hours at 1.5×106A/cm2 and 200°C. In addition, local hillocks and voids along the metal lines were observed. For Al(Cu,Si), the Al drift velocity was slowed down by Cu addition. The majority of hillocks started to grow at a distance about 6 μm away from the cathode end with current density of 1.5×106 A/cm2. The drift velocity of Al in Al(Cu,Si) was found to be a function of time starting with an initial low value and increasing to a an final steady-state value. The behavior was attributed to the migration of Cu and dissolution of Al2Cu precipitates. The activation energies of the depletion 3 Aμm of Al(2%,Cu, 3%Si) was determined to be 0.90±02 eV. The dissolution and growth of A12Cu in the tested samples of Ti/Al(2%Cu)/Ti/TiN were observed using the scanning electron microscope and an electron microprobe.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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References

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