Nitrogen plasma treatment for improving interface between etch stop layer and copper interconnect

Abstract

Interconnect structures exhibiting reduced accumulation of copper vacancies along interfaces between contact etch stop layers (CESLs) and interconnects, along with methods for fabrication, are disclosed herein. A method includes forming a copper interconnect in a dielectric layer and depositing a metal nitride CESL over the copper interconnect and the dielectric layer. An interface between the metal nitride CESL and the copper interconnect has a first surface nitrogen concentration, a first nitrogen concentration and/or a first number of nitrogen-nitrogen bonds. A nitrogen plasma treatment is performed to modify the interface between the metal nitride CESL and the copper interconnect. The nitrogen plasma treatment increases the first surface nitrogen concentration to a second surface nitrogen concentration, the first nitrogen concentration to a second nitrogen concentration, and/or the first number of nitrogen-nitrogen bonds to a second number of nitrogen-nitrogen bonds, each of which minimizes accumulation of copper vacancies at the interface.