In the formation of sub-micron pitch Direct Bond Interconnects (DBI), the inter-level dielectric (ILD) stack is highly heterogeneous to satisfy both electrical isolation and downstream planarization requirements P1.Following photolithography and the initial mask open steps (ILD 6-5 and 6-4), the ILD 6-3 Etch step serves as the primary bulk dielectric pattern transfer phase A1.It prepares the cavity for the eventual Cu pad that will undergo hybrid wafer-to-wafer bonding P4.By dividing the overall