Void Nucleation in Passivated Interconnect Lines: Effects of Site Geometries, Interfaces, and Interface Flaws

Stress driven nucleation of voids in passivated aluminum interconnect lines is analyzed within the context of classical nucleation theory. A discussion of sources of tensile stress in such lines leads to an upper limit of 2 GPa. Calculations suggest that even at this high stress, nucleation rates are far too low to account for observed rates of voiding. Void formation at a circular defect at the line/passivation interface is then considered. In this case, a flaw on the order of nanometers in size may develop into a void under the imposed stress. These results strongly suggest that void nucleation in aluminum interconnect lines can be controlled by eliminating defects in the line/passivation interface.