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Publications in Scientific Journals:

A. Bittner, N. Pagel, H. Seidel, U. Schmid:
"Long-term stability of Ag and Cu thin films on glass, LTCC and alumina substrates";
Microsystem Technologies - Micro- and Nanosystems - Information Storage and Processing Systems, 18 (2012), 879 - 884.



English abstract:
Silver (Ag) and copper (Cu) are regarded as
advanced material for metallization systems in microelectronic
devices because of their high electrical conductivity
and enhanced electromigration resistance. Typically,
organic circuit boards as well as ceramic and glass-ceramic
substrates use galvanic deposited Cu films or screen-printed
metallization for this purpose. When applying the latter
approach, however, the lateral resolution in the lm-region
being required e.g. for novel high frequency applications can
not be guaranteed. Hence, sputter deposition is envisaged for
the realization of thin film metallization systems. The reliability
of 300 nm thick Cu and Ag thin films is comparatively
investigated under accelerated aging conditions,
utilizing a test structure which consists of parallel lines
stressed with current densities up to 2.5 9 106 A cm-2 at
temperatures up to 300 C on Si/SiO2, glass, LTCC (low
temperature co-fired ceramics) and alumina substrates. To
detect the degradation via the temporal characteristics of the
current signal a constant voltage is applied according to the
overall resistance of the test structure. Knowing the mean
time to failure (MTF) and the activation energy at elevated
temperatures conclusions on the migration mechanism can
be drawn. Whereas on LTCC substrates the activation
energy Ea is about 0.75 eV for both Ag and Cu thin films, the
higher activation energies of about Ea * 1 eV measured for
Cu on glass and alumina indicate a suppression of back
diffusion especially at enhanced temperature levels. This
effect is predominantly caused by a stable oxide layer which
is formed at high temperatures and which acts as passivation
layer. Therefore, the overall electromigration resistance is
lower compared to Ag.

German abstract:
Silver (Ag) and copper (Cu) are regarded as
advanced material for metallization systems in microelectronic
devices because of their high electrical conductivity
and enhanced electromigration resistance. Typically,
organic circuit boards as well as ceramic and glass-ceramic
substrates use galvanic deposited Cu films or screen-printed
metallization for this purpose. When applying the latter
approach, however, the lateral resolution in the lm-region
being required e.g. for novel high frequency applications can
not be guaranteed. Hence, sputter deposition is envisaged for
the realization of thin film metallization systems. The reliability
of 300 nm thick Cu and Ag thin films is comparatively
investigated under accelerated aging conditions,
utilizing a test structure which consists of parallel lines
stressed with current densities up to 2.5 9 106 A cm-2 at
temperatures up to 300 C on Si/SiO2, glass, LTCC (low
temperature co-fired ceramics) and alumina substrates. To
detect the degradation via the temporal characteristics of the
current signal a constant voltage is applied according to the
overall resistance of the test structure. Knowing the mean
time to failure (MTF) and the activation energy at elevated
temperatures conclusions on the migration mechanism can
be drawn. Whereas on LTCC substrates the activation
energy Ea is about 0.75 eV for both Ag and Cu thin films, the
higher activation energies of about Ea * 1 eV measured for
Cu on glass and alumina indicate a suppression of back
diffusion especially at enhanced temperature levels. This
effect is predominantly caused by a stable oxide layer which
is formed at high temperatures and which acts as passivation
layer. Therefore, the overall electromigration resistance is
lower compared to Ag.


"Official" electronic version of the publication (accessed through its Digital Object Identifier - DOI)
http://dx.doi.org/10.1007/s00542-011-1402-z


Created from the Publication Database of the Vienna University of Technology.