Following Cu CMP and the subsequent cleaning of the first metal layer (M1), the exposed copper surface is highly susceptible to oxidation and constitutes a rapid diffusion path into subsequent dielectric layers P3.ILD 1-1 Deposition serves to create a multifunctional dielectric diffusion barrier (DB), etch stop (ES), and copper capping layer (CCL) prior to bulk dielectric deposition P3.Unlike the bulk ILD 1-2 layer deposited immediately afterward, ILD 1-1 must provide a dense, chemically stable