Suppression of stress induced open failures between via and Cu wide line by inserting Ti layer under Ta/TaN barrier

We verified the effect of Ti layer insertion on stress induced void formation in wide Cu lines where voids were formed under via. In order to improve adhesion property between via and underlying Cu, PVD-Ti was inserted under Ta/TaN barrier. When nominal 30 nm thick PVD-Ti layer was inserted (Ti thickness at via bottom was about 8 nm), the failure was sufficiently suppressed without degrading the electromigration resistance. In addition, the via resistance was reduced by 25% compared with conventional Ta/TaN barrier structure, while the Cu metal resistivity was unchanged by the Ti insertion.