Close atomic surface on aluminum alloy achieved by a near-neutral novel green chemical mechanical polishing method with high material removal rate

Abstract

Scratches, embedding of abrasives, and corrosion pits easily occur on the surface of aluminum (Al) alloy during traditional mechanical and chemical mechanical polishing (CMP). To achieve a close atomic surface on Al alloy, the material removal rate (MRR) is generally extremely low. To address these challenges, a near-neutral, novel green CMP slurry with a pH value of 6 was developed for Al alloy, consisting of silica, praseodymia, hydrogen peroxide, triethanolamine, and niacin. After CMP, a close atomic surface was achieved, with a surface roughness (Sa) of 0.231 nm in a scanning area of 50 × 50 μm², and the MRR was 12.56 μm h⁻¹. To the best of our knowledge, this MRR is the highest reported for such a close atomic surface on Al alloys. Transmission electron microscopy confirmed that the thickness of the damage layer was 6.9 nm. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy demonstrated that the Al alloy was oxidized by hydrogen peroxide, forming alumina and aluminum hydroxide, which dissolved into Al³⁺ ions and were chelated by niacin and triethanolamine. Consequently, chelating formulas were proposed. Our developed near-neutral green CMP provides a new approach to achieving a close atomic surface for soft and plastic Al alloys with a high MRR.