Ra. Augur et al., DIFFUSION AT THE AL AL OXIDE INTERFACE DURING ELECTROMIGRATION IN WIDE LINES/, Journal of applied physics, 79(6), 1996, pp. 3003-3010
Significant large-scale modification of the surface of Al-Si conductor
s was observed, due to electromigration in wide lines and under low st
ress conditions. After electromigration stressing the Al layers showed
local thickness variations, i.e., damage by thinning. The mechanism u
nderlying this damage causes substantial metal transport. Nevertheless
, damage by thinning has received little attention in the past. Thinni
ng was observed: (1) in a number of different alloys (Al-Si, Al-Cu, Al
-Si-V, and Al-Si-V-Pd), (2) with a number of different underlayers [Si
O2, W-Ti (no vacuum break after Al deposition) and W-Ti (oxidized surf
ace before Al deposition)], (3) over an extended temperature range, (4
) over a range of current density, and (5) in structures with and with
out passivation. The results show that thinning is a general phenomeno
n. An activation energy of approximately 0.5 eV was determined for the
temperature dependence of a combined mechanism of concurrent thinning
plus voiding in Al99S1. Several alternatives are examined to explain
the observations, namely mass movement along dislocations, Al bulk dif
fusion, and diffusion at the interface between the Al and its oxide. I
t is shown that diffusion at the Al/Al oxide interface most probably p
lays an important role in the damage mechanism, even under stress cond
itions where grain boundary diffusion is traditionally thought to domi
nate. Results also showed that alloying of Al with Pd can reduce the e
ffects of damage by thinning. (C) 1996 American Institute of Physics.