A chemical mechanical polishing (CMP) apparatus includes a polishing pad located on a top surface of a platen configured to rotate around a vertical axis passing through the platen, a wafer carrier configured to hold a substrate on a bottom surface thereof and to press the substrate on a top surface of the polishing pad, a slurry dispenser configured to dispense slurry over the top surface of the polishing pad, and a pad conditioning unit comprising a pad conditioning disk and a conditioning head configured to hold the pad conditioning disk. The conditioning head includes an electromagnet and the pad conditioning disk comprises a first ferromagnetic material portion configured to be attracted to the electromagnet when the electromagnet is energized.