Effects of pre-existing interfacial defects on the stress profile in aluminum interconnection lines

The profile of thermal stresses in aluminum interconnection lines, with the presence of local debonded areas between the line and the surrounding dielectric, is studied numerically. Local interfacial debonding is presumably due to contamination during the line patterning process. Various geometrical features of the interconnect and the debond segment are assumed, and the resulting stress fields are examined through two-dimensional (2-D) and three-dimensional (3-D) finite element analyses. It is found that interfacial debonding results in a local reduction of stress in aluminum, with the effect becoming larger as the line aspect ratio increases. The location of debond also influences the line stress. Implications of the findings to the interconnect reliability, particularly stress-induced voiding in aluminum lines, are discussed.