Plasma damage and metal ion penetration are critical issues for porous low-dielectric-constant (low-k) materials used in the back-end-of-line interconnects. This study proposed a novel process with in-situ repairing plasma-induced damage and capping a barrier for porous low-k materials by Hexamethyldisilazane (HDMS) plasma treatment. For a plasma-damaged porous low-k material, its surface hydrophilic state was transformed to hydrophobic state by HDMS plasma treatment, revealing that damage was repaired. Simultaneously, a dielectric film was capped onto the porous low-k material, and displayed better barrier capability against Cu migration. Additionally, the breakdown reliability of the stacked dielectric was enhanced by the means of HDMS plasma treatment. The optimized HDMS plasma treatment time was found to be 10 s. Therefore, this proposed HDMS plasma treatment processing is a promising technique for highly applicable low-k material used for advanced technology nodes.