Reliability Challenges in Copper Metallizations arising with the PVD Resputter Liner Engineering for 65nm and Beyond

In this paper the influence of liner deposition parameters on the reliability of 65nm copper metallizations have been investigated for two different deposition sequences. The use of resputter liners in the 65nm generation turned out to change the via-voiding failure mode qualitatively from voiding at the very via-bottom to void nucleation at mid-half of the via. In addition, the resputter intensity and liner thickness have a quantitative impact on the electromigration (EM) failure times and stressmigration (SM) failure rates. For a given liner thickness an increasing resputter intensity turned out to improve the overall reliability as a result of a more pronounced anchoring of the via within the metal line underneath. In terms of the liner thickness, thinner barriers yield in general reduced failure times. However, this loss can be compensated at least partially by adjusting the resputter intensity with repsect to the specific liner thickness.