Electromigration failure in Al interconnects is one of the serious concerns especially for sub-half micron devices reliability. The margin is abruptly decreased as the shrinkage of the design rule proceeds because of the inverse square dependence of the lifetime on the current density. This work aims to improve EM lifetime and, as result, to extend its applicability to sub-half micron era. One of the approaches to improve E.M. resistance is increasing copper doping concentration in the aluminum metal film. In addition, recovering existence of the damaged layer at the surface of TiN after tungsten etching back (W-EB) process is also crucial because poor (111) crystalline alignment of AlCu has been attributed to this damaged layer of TiN underlayer. The 1percent copper aluminum alloy gets better E.M. resistance than that of 0.5percent copper aluminum alloy. And with TiN re-deposition gets even better results than that without TiN re-deposition.
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