TITLE

Reduction in flux divergence at vias for improved electromigration in multilayered AlCu interconnects

AUTHOR(S)
Ting, Larry; Hong, Qi-Zhong; Hsu, Wei-Yung
PUB. DATE
September 1996
SOURCE
Applied Physics Letters;9/30/1996, Vol. 69 Issue 14, p2134
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Using of W-plug vias in AlCu interconnects is known to significantly degrade electromigration (EM) performance because W is a diffusion barrier and prevents the depleting species by EM from being replenished at the via. In the present study, we demonstrate that this problem of limited source for EM migrating species can be dramatically alleviated in a multilayered metallization of TiN/AlCu/TiN using Al-plug vias. EM lifetime improvements as large as by an order of magnitude are accomplished by reducing the flux divergence at the Al-plug via. This flux divergence is critically determined by the effective thickness of some transition metal films at the via, which include a Ti/TiN stack for the via barrier and a TiN layer of antireflection coating for the bottom level metal lead. Scanning electron microscopy failure analysis also verifies that the samples with W-plug vias have the void damages consistently located at the via. For the samples with Al-plug vias and with the flux divergence at the via being largely reduced, the void failures locate on the metal lead and no visible damage at or within the via, indicating the reduced flux divergence at the via has become smaller than those generated on the metal lead due to microstructural variations. © 1996 American Institute of Physics.
ACCESSION #
6290450

 

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