Additional microstructural analysis on the samples examined in the paper 'Are high resolution resistometric methods really useful for the early detection of electromigration damage?'

In a previous paper (A. Scorzoni, S. Franceschini, R. Balboni, M. Impronta, I. De Munari, and F. Fantini, Are high resolution resistometric methods re ally useful for the early detection of electromigration damage? Microelectr . Reliab, 1997;37(10/11):1479-1482), we reported largely different electrom igration lifetimes and different high resolution early resistance changes m easured on two nominally identical lots of 4 mu m wide lines tested at mode rately accelerated stress conditions. A microstructural analysis on unstres sed samples was performed in order to detect the reason which induced these differences. The analysis confirmed a major defectivity of the lot with sh orter lifetime: we detected the presence of TiAl3 precipitates at the inter face between the Al-Cu and the Ti-based metal barrier. This was not easily detectable by means of simple visual inspection. These additional findings confirm that a quick electrical detection of the metallization quality coul d be feasible by means of high resolution resistance measurements without t he need of time-consuming direct examination of production lots. (C) 1999 E lsevier science Ltd. All rights reserved.