Share Email Print
cover

Proceedings Paper

Electromigration in VLSI metallization
Author(s): Thomas Kwok
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

There are increasing reliability concerns of electromigration-induced and thermal stress-induced failures in submicron interconnects carrying the projected high current density and in multilevel interconnection with W studs. Electromigration characteristics of Al and Al-Cu submicron lines, two level Al-Cu lines with W studs, Al fine lines under pulsed current stressing at high frequencies, and Al and Al-Cu fine lines under temperature cycling have been systematically studied. Lifetime is affected by grain size, grain morphology and bend structure in submicron metal lines. The lifetime of W stud chains is less than a half of that of Al-Cu flat lines. The discontinuity of Cu supply at Al-Cu/W interfaces account for most of the reduction in the electromigration resistance of W stud chains. Under pulsed current stressing at frequencies 50-200 MHz, our data indicate no threshold frequency for drastic change in lifetime. However, lifetime increases with duty cycle as tso cc r- Z.', which is a remarkable improvement over an av¬ erage current density model. Lifetime also depends explicitly on both current on-time and current off period. The extra thermal stress induced by temperature cycling shortens the lifetime of both Al and Al-Cu fine lines by more than an order of magnitude. Our results also show that the addition of Cu in Al fine lines improves the resistance to thermal stress-induced failures, probably by the suppression of grain boundary sliding and migration.

Paper Details

Date Published: 1 December 1991
PDF: 12 pages
Proc. SPIE 1596, Metallization: Performance and Reliability Issues for VLSI and ULSI, (1 December 1991); doi: 10.1117/12.51012
Show Author Affiliations
Thomas Kwok, IBM/Thomas J. Watson Research Ctr. (United States)


Published in SPIE Proceedings Vol. 1596:
Metallization: Performance and Reliability Issues for VLSI and ULSI
Gennady Sh. Gildenblat; Gary P. Schwartz, Editor(s)

© SPIE. Terms of Use
Back to Top