A study of the failure mechanism of a titanium nitride diffusion barrier

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Abstract
TiN has been popularly used as a diffusion barrier between Al and Si to prevent “spiking.” It has, however, been reported that spiking still occurs through TiN at temperatures higher than 500 °C. In this study, we investigated the mechanism of spiking through TiN using high resolution transmission electron microscopy and electron dispersive spectroscopy (EDS). We found TiN to be saturated with Al upon annealing at 550 °C. Si also diffuses through TiN and dissolves into Al. Spikes form upon 550 °C annealing at the Si substrate. EDS analysis revealed the phase of the spikes to be Al3Ti containing a considerable amount of Si. These results indicate that spiking through TiN is due to the formation and growth of Al3Ti after the Al saturation at the bottom of TiN. We discuss these results based on the Al–Ti–Si and Al–Ti–N ternary phase diagrams.