Study on Chemical Action Mechanism of Ferric Chloride-Based Polishing Slurry in CMP of 304 Stainless Steel

The type 304 stainless steel will be widely applied as one of the substrate materials of the flexible displays. In this paper, many experiments using chemical mechanical polishing (CMP) slurry with the FeCl3 oxidant at different pH values were studied in the material removal rate (MRR) and the surface roughness. Chemical action mechanisms about the Fe3+, the H+, the OH− and the Cl− in the CMP slurry was also studied in the CMP of 304 stainless steel. These research results show that the ion Fe3+ can react with the iron, the nickel and the chromium in the 304 stainless steel to produce the ferrous chloride. The ion Cl− can react with metal ions, such as the Fe2+, the Fe3+ and the Ni2+ to form a soluble complex ion and improve the MRR. The higher the concentration of the ion H+ in the CMP slurry is, the stronger the etching effect of the ion H+ on the 304 stainless steel will be. It can inhibit the hydrolysis of the FeCl3 to form the Fe(OH)3 precipitation, and increase the concentration of the Fe3+ in the CMP slurry and the MRR. The ion OH− in the CMP slurry can react with the Fe3+ to form the Fe(OH)3, which reduced the concentration of the Fe3+ in the CMP slurry and the MRR