ANALYSIS OF STRESS-INDUCED VOID GROWTH MECHANISMS IN PASSIVATED INTERCONNECT LINES

Simple theoretical models have been used to investigate four possible mechanisms of void growth in interconnect lines with a bamboo grain structure. The mechanisms considered are: creep deformation by dislocation motion; grain-boundary diffusion; diffusion along the interface between the line and the surrounding passivation; and void growth by lattice diffusion. The results show that all four mechanisms may cause the void to grow, but any one mechanism operating alone gives rise to slow or negligible rates of growth; however, plastic creep flow and grain-boundary diffusion may act in a cooperative manner, which causes rapid void growth. It is shown that the extent of coupling between diffusion and creep increases as the linewidth is reduced. Finally, the numerical calculations are used to estimate the time required for the line to fail, as a function of temperature and linewidth. The predictions are shown to be consistent with observations reported in the literature.