Design of ECP additive for 65 nm-node technology Cu BEOL reliability

In this work, the design criteria of ECP additives on Cu BEOL reliability are revealed. By varying the ECP additive structures and concentrations, we demonstrate how gap filling performance and impurity level of the bulk copper can influence the electromigration lifetime and stress induced void (SIV) formation. It was found that the impurity in the grain boundary could act as an effective vacancy diffusion barrier to inhibit SIV formation. However, ECP additive conditions that produce highly impure Cu was found to increase the gap filling pits on top of the sub-micron features that would reduce the electromigration (EM) lifetime performance. By proper design of ECP additives, high impurity incorporation in the wide metal line without gap filling pit formation can be achieved. The stress SIV formation was inhibited with excellent EM resistance.