Following the Metal 3 Cu electroplating deposition, the wafer surface is covered with a thick blanket of excess copper (overburden) that must be removed to physically isolate the individual interconnect lines P1.This Cu CMP step is the first phase of the dual-step planarization sequence, specifically targeting the rapid removal of bulk copper while deliberately stopping at the underlying Ta-based liner A2.It is distinct from earlier lower-level Cu CMP steps (such as step #222) because Metal 3 ty