Thermomechanically induced voiding of Al-Cu thin films

It is now recognized that voiding failures in Al-Cu interconnects in integrated circuits are due to the high residual stresses developed as a result of thermal expansion mismatch between A1 and Si or SiO₂. In this paper, we review some of the current theoretical developments in calculating times to failure for these interconnects. Thermal cycling experiments were performed to determine times to failure under different testing conditions. These results were then compared with the recent theory developed here at Northwestern. It is based on consideration of grain- boundary and surface diffusion and fracture mechanics. The theory appears to give predictions that agree very well with experiments.