The ILD 2-2 Deposition step serves as the primary bulk inter-layer dielectric separating Metal 2 and Metal 3, defining the critical Via 2 height A2.It is preceded by the MET2 chemical-mechanical polishing (CMP) and the deposition of ILD 2-1, which often acts as a thin cap or etch stop layer to prevent copper diffusion into the bulk dielectric P4.ILD 2-2 provides the structural matrix for the upcoming Via 2 dual-damascene patterning steps (Engineering Practice).Unlike upper-level dielectrics such