Study of void growth in 120 nm copper lines by in situ SEM

The electromigration-induced void dynamic in 120 nm Cu lines is studied in situ inside a SEM. The evolutions of the void shape and growth rate are detailed, and compared to finite-element modeling (FEM). In the case of Cu/porous ULK lines with Ta/TaN barrier, the void is found to nucleate from the top corner edge. The shape gradually evolves from round to triangular up to rectangular, in qualitative agreement with simulations. For a current density of 50 MA cm−2, the transversal and longitudinal void growth rates are found nearly constant.