Copyright © (2002) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics
The electrical resistivity of thin films of Ta and TaN has been examined as a function of film
thickness and other processing parameters. The films were deposited by magnetron sputtering of
Ta cathodes with Ar, or mixtures of Ar and N2 for the case of TaN. The TaN films were
deposited in a broad range of compositions, depending on reactive gas flow and system
configuration, and showed strong increases in resistivity as thickness was decreased. Ta films
deposited on silicon dioxide or Cu surfaces were always beta-phase, and showed little resistance
increase as the thickness was reduced. Ta films deposited on TaN with greater than 30% N and
with thickness greater than 2 nm were alpha phase, and showed significant increases in resitivity
as thickness was reduced. The application and electrical properties of these films as diffusion
barriers in interconnect structures will depend strongly on the thicknesses at the contact points at
the bottoms of vias and only weakly on the phase of the Ta. The resistivity of the barrier films on
via and trench sidewalls is high enough to be irrelevant to circuit performance.
By: Stephen M. Rossnagel
Published in: Journal of Vacuum Science and Technology B, volume 20, (no 6), pages 2328-36 in 2002
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