Untersuchung der Degradation von elektrisch gestresstem nano-porösem ultra low-k Dielektrikum vor dem elektrischen Durchschlag

Nano-porous ultra low-k dielectrics
are important materials for high-speed
integrated circuits. They enable low line
capacitances, but show poor mechanical
properties compared to conventional oxide.
This work describes for the first time the
intrinsic degradation in nanometer scale after
electrical stress stopped before a breakdown
occurs. By means of tip type electrode test
structures, specifically designed for this
investigation and processed in commercially
available semiconductor technology, electrical
stress and physical analysis have been performed
to show degradation patterns.
The results show a typical leakage current curve
and a formerly unknown dynamic shrinking of the
dielectric leading to the development of bubble-shaped
holes near the anode. Starting at the anode, tantalum
transport into the dielectric has been found.
it is assumed, that under operating conditions after
some time, shrinking of the dielectric leads to an
equilibrium of voids and denser dielectric including
fixed oxidized tantalum.