Following the Chemical Mechanical Planarization (CMP) and subsequent cleaning of the Metal 2 (Cu) layer, the ILD 2-1 Deposition step serves as the critical copper capping layer and diffusion barrier P2.In the back-end-of-line (BEOL) process flow, this dielectric barrier must immediately cover the exposed Cu to prevent its oxidation and diffusion into the subsequent interlayer dielectric (ILD 2-2) P3.Furthermore, this layer functions as an etch stop during the downstream VIA 2 patterning process