T. J. Barbieri, J. Wang, M. Kottke, D. Theodore, Freescale Semiconductor, Inc., Tempe, AZ; R. Wetz, Tyco Healthcare, Boulder, CO

Summary: In the analysis described in this paper, multiple parts failed during a 96 hour HAST (highly accelerated stress test) run. FA of the failed parts identified an indirect method of identifying low-grade electrical overstress (EOS) on thin, top-layer aluminum metal lines with TiN anti-reflective coating (ARC). Visual inspection suggested that passivation and ARC had been removed from several top-metal lines due to their optical appearance. SEM inspection found that this was not true. Passivation was observed to be intact, but cracked. A series of experiments utilizing FIB cross-sections, Auger mapping, Auger depth profiling, TEM inspection and EDS were used to show that the TiN had not been removed; it had, in fact, been oxidized, which resulted in the change of appearance.