B. T. Gillette, Fairchild Semiconductor Corp, Mountaintop, PA

Summary: Inductive Life Stress devices in a deteriorated state were encountered at the 168 hour read during experimental testing. A metal grain boundary breakdown mechanism was found during the analysis of the device, which was creating a gross electrical short gate to source and gate to drain. The AlSiCu top metal was breaking down along the grain boundaries. There was alloying of the source Al bondwire into the substrate. This alloying was creating a short to the gate, source, and drain. Several variations in the metal stack and testing conditions were evaluated to better understand the cause of the devices inability to with stand Inductive Life stress and to provide a process solution. The prevention of the AlSiCu top metal grain boundary breakdown during inductive life stress testing required a die size and testing condition change. This change resulted in a reduced grain boundary breakdown and consequently prevented Al grain boundary breakdown, TiW barrier breakdown and Al spiking induced metal breakdown mechanism. The die change and modified testing conditions resulted in a successful pass through the inductive life stress testing.