Solid-Phase Reactions in Al Alloy/TiN/Ti/Si Systems Observed by In Situ Cross-Sectional TEM

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Abstract
The mechanism of solid-phase reactions for multilayers of Al-1%Si-0.5%Cu/TiN/Ti/n+-Si substrates has been investigated by means of in situ and high-resolution/analytical cross-sectional transmission electron microscopy (X-TEM). We have succeeded for the first time in real-time observation of the instant of barrier breakdown of the TiN layer. An intermediate Al-Ti-Si(-N) layer ( ∼4 nm thickness) composed mainly of microcrystallites was formed at the Al alloy/TiN interface at ∼450° C, and the microcrystalline phase grew along the TiN grain boundaries. At over ∼500° C, the Al diffused downward very rapidly through the TiN layer, forming an Al region under the TiN layer. It is concluded that the rapid redistribution of the Al may be caused by movement along the TiN grain boundaries in the microcrystalline state.