Abstract :
Channeling cracks in brittle thin films have
been observed to be a key reliability issue for advanced
interconnects and other integrated structures.Most theoretical
studies to date have assumed no delamination
at the interface, while experiments have observed channel
cracks both with and without interfacial delamination.
This paper analyzes the effect of interfacial
delamination on the fracture condition of brittle thin
films on elastic substrates. It is found that, depending
on the elastic mismatch and interface toughness,
a channel crack may grow with no delamination, with
a stable delamination, or with unstable delamination.
For a film on a relatively compliant substrate, a critical
interface toughness is predicted, which separates
stable and unstable delamination. For a film on a relatively
stiff substrate, however, a channel crack grows
with no delamination when the interface toughness is
greater than a critical value, while stable delamination
along with the channel crack is possible only in a small
range of interface toughness for a specific elastic mismatch.
An effective energy release rate for the steadystate
growth of a channel crack is defined to account
for the influence of interfacial delamination on both the
fracture driving force and the resistance, which can be
significantly higher than the energy release rate assuming
no delamination.
