Benefit of post etch treatment for defectivity improvement in the BEOL

In the challenging context of backend integration, the trench first hard mask architecture demonstrated its interest as the cost efficient solution for volume manufacturing as well as the time effective solution for yield learning. One major challenge using such integration is the metal fluoride crystal formation after etching leading to line and via opens. In this paper we demonstrate that this crystal growth is strongly dependent on the etch chemistry while wet cleaning is inefficient to remove them. In situ post etch treatment addition after etching is then a mandatory solution to prevent their formation as well as cure other defects like copper extrusion.