Following Cu CMP, the bulk Cu overburden is removed, leaving the Ta-based liner exposed on the field dielectric P1.The Ta-based liner CMP step, often termed barrier CMP, is required to remove this remaining liner and polish the entire interconnect stack P1.This process electrically isolates the MET4 copper lines by clearing conductive material from the field dielectric, preventing short circuits between adjacent lines A1.It prepares a globally planarized surface, encompassing Cu in trenches, sid