[Zurück]

A. Bittner, H. Seidel, U. Schmid:
"Electromigration resistance and long term stability of textured silver thin films on LTCC";
Microelectronic Engineering, 88 (2010), 1; S. 127 - 130.

Silver (Ag) is regarded as advanced material for metallization purposes in microelectronic devices
because of its high conductivity and its enhanced electromigration resistance. Besides the typical use
of silicon based substrate materials for device fabrication, thin film metallization on ceramic and
glass-ceramic LTCC (low temperature co-fired ceramics) substrates gets more and more into focus as
only thin film technology can provide the required lateral resolutions of structures in the lm-range
needed for e.g. high frequency applications. Therefore, the reliability of Ag thin films is investigated under
accelerated aging conditions, utilizing test structure which consists of 5 parallel lines stressed with current
densities up to 1.5 107 A cm 2 at temperatures ranging from room-temperature up to 300 C. To
detect the degradation via the temporal characteristics of the current signal a constant voltage is applied
taking the overall resistance of the test structure into account. The mean time to failure of the Ag metallization
substantially depends on the degree of (1 1 1)-orientation which, in turn, is strongly affected
by the plasma power PP during deposition. Therefore, Ag thin films deposited at PP = 1000W feature a
7 times higher reliability than those deposited at PP = 100 W. Due to the enhanced stability of grains
being (1 1 1)-oriented in textured thin films the material transport predominantly occurs along grain
boundaries, whereas in Ag films without a (1 1 1)-orientation volume-related diffusion effects dominate
due to the lower stability of these grains.

Silver Thin film LTCC Electromigration Reliability

http://dx.doi.org/10.1016/j.mee.2010.09.018