Ag. Domenicucci et al., EFFECT OF COPPER ON THE MICROSTRUCTURE AND ELECTROMIGRATION LIFETIME OF TI-ALCU-TI FINE LINES IN THE PRESENCE OF TUNGSTEN DIFFUSION-BARRIERS, Journal of applied physics, 80(9), 1996, pp. 4952-4959
A systematic study was performed of the microstructural and electromig
ration characteristics of Ti-Al(Cu)-Ti laminate structures fabricated
from two metal wiring levels 1 mu wm in width. The total Cu content in
the Al(Cu) core layers was varied from 0.5 to 2.0 wt %. A high degree
of [111] texture was found for all Cu concentrations except for the 0
.5 wt % film. Grain size statistics were found to be independent of th
e Cu concentration. The Al grains were supersaturated with Cu which le
d to shifts in resistance during low temperature baking and electromig
ration testing. The electromigration lifetime of stripes connected to
large reservoirs of Cu and Al was found to be linearly dependent on th
e total Cu content, whereas there was a ''roll off'' in the lifetime o
f two-level W stud structures as the Cu content was increased. The act
ivation energy for electromigration induced failure was found to be 0.
78-0.93 eV. Resistance shifts during electromigration and temperature
only stressing and the microstructural characteristics of failed struc
tures were explained in terms of the distribution of Cu in the Al matr
ix and the geometry of the structures using a blocking boundary model.
(C) 1996 American Institute of Physics.