A model for electromigration failure distributions of contacts andvias in advanced IC technologies
Oates, A.S.
Bell Labs., Lucent Technol., Orlando, FL;
Abstract
Electromigration failure of contacts and vias in deep submicron IC
technologies is the key concern for interconnect reliability. We present
a physical model for electromigration failure of contact and vias in
deep submicron technologies. We show that this model can be used to
develop a complete description of the behavior of failure distributions
of contacts and vias that is in very good agreement with experimental
observations. The basic premise of the model is that failure is
controlled by the electromigration-induced drift of the conductor away
from the contact or via. The failure time of the contact or via is
determined by the drift velocity of the conductor and the contact or via
geometry. The model predicts that the median time-to-fail (MTF) exhibits
a 1/(j-jc) dependence on current density. Most significantly,
however, the model shows that the lognormal failure time dispersion, a
also exhibits a 1/(j-jc) dependence, as well as a strong
temperature dependence, and that these effects are inherent properties
of contacts and vias. We compare model predictions for failure
distributions to experimental data to establish the validity of the
drift model
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