In the dual-damascene sequence of the Metal 2 (MET2) module, the bulk copper overburden is first planarized during the main Cu CMP step P3.Following this, the Ta-based liner CMP step is executed to completely remove the exposed Ta/TaN barrier layer from the field dielectric regions P3.This step is critical because leaving any conductive liner residue on the field oxide would result in electrical shorting between adjacent MET2 lines (Engineering Practice).Furthermore, this barrier CMP step planar