G. Harsanyi, Copper may destroy chip-level reliability: Handle with care - Mechanism and conditions for copper migrated resistive short formation, IEEE ELEC D, 20(1), 1999, pp. 5-8
Although copper has a number of advantageous parameters in comparison with
aluminum, and therefore, is expected to become the metallization of future
high-speed, high-density silicon devices, its application introduces a new
failure mechanism into the systems which has never occurred with aluminum;
this is the electrochemical migration (not equal to the electromigration) r
esulting in short circuit formation between adjacent metallization stripes
under DC bias, A great alert signal must be given for semiconductor produce
rs in order to perform lifetime tests before introducing copper into the ev
eryday fabrication process, otherwise the reliability of future electronic
systems may dramatically be destroyed.