XPS study of CMP mechanisms of NiP coating for hard disk drive substrates

Chemical mechanical polishing (CMP) mechanisms of NiP coating plated on Al–Mg alloy substrates have been investigated with an X-ray photoelectron spectroscope (XPS). The XPS results indicate that after cleaning, the disk surface contains a thin layer of Ni(OH)2 and P2O3, followed by a thin NiO and P2O3 layer. It is also deduced that during polishing, the disk surface has an oxidization layer with Ni2+ and P3+ species. The experimental investigations reveal that the CMP mechanisms involve a simultaneous process of surface chemical passivation and nano-particle wear.