Novel green chemical mechanical polishing for an aluminum alloy and mechanisms interpreted by molecular dynamics simulations and measurements

Aluminum (Al) alloy is a kind of soft-plastic metal, and traditional chemical mechanical polishing (CMP) is easy to produce scratches on the polished surface and embed of abrasives, resulting in the degradation of devices. In addition, conventional CMP generally employs toxic and corrosive slurries, leading to the pollution of environment. To address these challenges, a novel green CMP was developed for Al alloy, consisting of ceria, silica, sodium carbonate, hydrogen peroxide, glycine and deionized water. After CMP, surface roughness Sa is 0.258 nm under an area of 100 × 100 μm2, which is the lowest surface roughness reported previously in such a big measurement area for Al alloy. Transmission electron microscopy confirms that the thickness of damaged layer is merely 4.6 nm. X-ray photoelectron microscopy and Fourier transform infrared spectroscopy reveal that composite abrasives are conducive for the generation of Al-O, Al-O-Si and Ce-Al bonds on the polished surface. Molecular dynamics simulations elucidate that the subsurface damage is mainly caused by exerted loading of abrasives on amorphous layer, as well as vacancy induced through the annihilation of dislocations profoundly. These outcomes provide a new avenue to manufacture atomic surfaces of soft-plastic metals for latent applications in devices.