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

We measured electromigration incubation time and ionic drift velocity of copper interconnect using the Kawasaki-Hu test structure in the temperature range of 255-350°C. 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/cm². Measured results indicate a remarkable incubation time of void growth in the direction of line, and it depends on the square of the current density. On the other hand, the drift velocity appears to be a linear dependent of current density. Consequently, both contributions must be considered in the lifetime estimation of operating condition. The critical product of the test structure is 7735A/cm at 300°C.