Electromigration of Al-0.5 wt%Cu with Nb-Based Liner Dual Damascene Interconnects

概要

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The electromigration (EM) of Al-0.5 wt%Cu/Nb-based liner dual damascene (DD) interconnects is investigated for the first time. It is found that EM-induced voids nucleate in the line around the via at the cathode end of the line and their number decreases as the distance from the via becomes longer for the tungusten (W)-single damascene (SD)/aluminum (Al)-dual damascene (DD) interconnects. This fact indicates W-SD/Al-DD interconnects has mono-modal EM failure. Regarding the Al-SD/Al-DD interconnects, two types of layered liner, niobium (Nb)/long throw sputtered (LTS)-niobium nitride (NbN)/Nb and Nb/self ionized sputtered (SIS)-NbN/Nb, are applied and the EM failure mode is investigated. It is found that the Nb/LTS-NbN/Nb liner sample has bi-modal failure, which manifests as normal failure similar to W-SD/Al-DD interconnects and failure with long time to failure (TTF), probably due to the continuous atom flow at the sidewall or bottom of the via in the lower Al-SD interconnects. On the contrary, the Nb/SIS-NbN/Nb liner sample has mono-modal failure with a tight distribution of the EM log-normal distribution, resulting in a high EM reliability.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2004-10-15