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Barrier Properties of Amorphous Binary Ta-Ni Thin Films for Cu Interconnection.

Authors :: Fang, J. S.
Hsu, T. P.
Chen, H. C.
Source :: Journal of Electronic Materials; May2007, Vol. 36 Issue 5, p614-622, 9p, 5 Black and White Photographs, 6 Graphs
Publication Year :: 2007
Abstract: Highly thermally stable amorphous Ta<subscript>x</subscript>Ni<subscript>1-x</subscript> (x = 0.25 and 0.75) thin films were deposited on Si and Si/SiO<subscript>2</subscript> substrate by magnetron dc sputtering, and the performance of films (20-nm thick) as barriers for copper (Cu) interconnection was evaluated. The failure behaviors of the films were elucidated using a four-point probe, x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Auger emission spectrometry (AES). A highly (111) textured Cu film could be obtained when Cu was deposited on Si/Ta<subscript>0.25</subscript>Ni<subscript>0.75</subscript> and Si/SiO<subscript>2</subscript>/Ta<subscript>0.25</subscript>Ni<subscript>0.75</subscript> substrates. The failure temperatures of Si/Ta<subscript>0.25</subscript>Ni<subscript>0.75</subscript>/Cu- and Si/Ta<subscript>0.75</subscript>Ni<subscript>0.25</subscript>/Cu-stacked films were 550°C and 600°C, respectively. Failure of the studied films initiated the penetration of Cu into the Si/Ta<subscript>x</subscript>Ni<subscript>1-x</subscript> interface and triggered the partial dissociation of the Ta<subscript>x</subscript>Ni<subscript>1-x</subscript> barrier layer, forming Cu<subscript>3</subscript>Si precipitates, Ni-silicide and Ta-silicide. Increasing the Ta content enhanced the microstructural and thermal stability of the stacked films, markedly improving barrier properties. The experimental findings demonstrated that the barrier characteristic of Ta<subscript>0.75</subscript>Ni<subscript>0.25</subscript> was substantially superior to that of Ta<subscript>0.25</subscript>Ni<subscript>0.75</subscript>. [ABSTRACT FROM AUTHOR]