Electromigration induced incubation, drift and threshold in single-damascene copper interconnects

We measured electromigration incubation time and ionic drift velocity of copper interconnect using Kawasaki-Hu test structure (1) in the temperature range of 255-350degreesC. To estimate the electromigration threshold product of current density and line length, electromigration tests were performed with current densities in the range of 1.9-7.7 MA/cm(2). Measured results indicate remarkable incubation time of void growth in the direction of line, and it depends on a square of current density. On the other hand, drift velocity appears to be a linear dependent of current density. Consequently, both contributions must be considered on lifetime estimation of operating condition. The critical product of the test structure is 7735A/cm at 300degreesC.