Annealing effects on interfacial fracture of gold-chromium films in hybrid microcircuits

In this study, stressed overlayers and nanoindentation were used to study the effect of elevated temperature on the resistance to interfacial fracture of gold-chromium films in hybrid microcircuits. The samples were prepared by sputter deposition of gold films and chromium adhesive layers onto sapphire substrates. Some films were left in the as-deposited condition for testing. Others were annealed until either most or all the chromium adhesive layer had diffused from the substrate interface. Stressed overlayers and nanoindentation were then used to drive interfacial delamination and blister formation. From these blisters, interfacial fracture energies were determined using mechanics-based models modified for multilayer film effects. The results clearly showed that the chromium interlayers increased interfacial fracture energy. However, they showed an even greater increase in fracture energy after diffusion had reduced the continuous chromium adhesion layer to a solid solution of gold and chromium, suggesting two different mechanisms act to control resistance to interfacial fracture in these films.

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