Fenton reaction chemical mechanical polishing liquid composition optimization of polishing GaN wafer

Aiming at the polishing liquid used for polishing GaN wafers by Fenton reaction CMP, a parameter optimization experiment was carried out with the surface quality as the evaluation index, and the optimal ratio of the polishing liquid components was found out. The results show that when the mass fraction of H₂O₂ is 7.5%, the surface of GaN wafer processing is the best, and the surface roughness reaches 3.2 nm; the catalyst can effectively adjust the rate of the Fenton reaction. Compared with the liquid catalyst FeSO₄ solution and the solid catalyst Fe₃O₄ powder, the solid catalyst Fe₃O₄ powder can continuously ionize Fe²⁺ in the solution, so that the Fenton reaction can continue to work throughout the process. When the particle size of Fe₃O₄ powder is 20 nm, the polishing surface is the best, and the surface roughness reaches 3.0 nm; compared with alumina, cerium oxide, and silica sol abrasives, the best surface polishing effect can be achieved while using the silica sol abrasives, and the surface roughness reaches 3.3 nm; when the mass fraction of silica sol abrasive is 20.0% and the abrasive particle size is 60 nm for polishing, the surface roughness reaches 1.5 nm. After optimizing the composition of the polishing liquid, the GaN wafer was polished with the optimal composition parameters of the polishing liquid, and a smooth surface with a surface roughness of 0.9 nm could be obtained.