Following the deposition of the Ta-based liner, Cu seed, and the bulk Metal 1 (M1) Cu electroplating, the Cu CMP step is deployed to remove the bulk Cu overburden and define the isolated M1 interconnect lines P1.This specific step focuses exclusively on clearing the excess copper while deliberately stopping on the underlying Ta-based liner, which constitutes the first phase of the two-step interconnect planarization process P1.By doing so, it planarizes the wafer surface and prepares the structu