Chemical Mechanical Polishing of Aluminum Alloys using Alumina-Based Slurry

Chemical mechanical polishing has become potential global planarization technology for metal alloy. In this paper, we reported the CMP performances of aluminum alloy using alumina-based slurry. The influence of abrasive size, dispersant concentration (weight fraction) and pH-controlling agents on CMP performances were investigated, respectively. It is found that, with the particle size increased, the material removal rate and average surface roughness increased, while the glossiness decreased. When the weight fraction of PEG-600 reached 0.5% (weight fraction), the minimum R_a and the best glossiness can be achieved. Among kinds of the pH-controlling agents, citric acid proved to be efficient for lowest statics etch amount, highest MRR and best glossiness. In addition, the static etch and CMP mechanisms of alumina-based slurry were briefly discussed. The mechanisms revealed that citric acid on Al alloy CMP performance: responsed to combined effects of corrosion and chelation. The optimized alumina-based slurry ingredient was Al₂O₃, 3.3 μm; H₂O₂, 4%; PEG-600, 0.5%; H₃Cit, 1.5%. This is different from the traditional polishing, in which hazardous chemicals HNO₃ and H₂SO₄ were used for Al alloys.