Photo-Assisted Chemical Mechanical Polishing of Si Wafer Using Phosphorescent Particles as a Luminescent Agent

Chemical mechanical polishing (CMP) is used for fabricating semiconductor wafer surfaces because it produces smooth and damage-free surfaces. Polishing efficiency is a key factor to decrease fabrication costs. Photo-assisted CMP—a promising method to improve polishing efficiency—requires a special setup allowing the material surface to be directly illuminated by the excitation light, which increases initial setup costs. Thus, a photo-assisted method that improves polishing efficiency without a special setup is strongly desired. We report a photo-assisted CMP method that employs phosphorescent particles (PhPs). X-ray analysis demonstrates that the Si surface is oxidized by photo-chemical treatment using PhPs. Further, photo-assisted CMP using PhPs added into a polishing slurry improves the material removal rate for Si under UV irradiation on the polishing pad; however, large and blocky PhPs generate defects on the polished surface. A double-layered polishing pad (abrasive layer partly stacked on the phosphorescent layer) is proposed to obtain smooth and defect-free surfaces. Compared with conventional CMP, photo-assisted CMP using the double-layered pad achieves higher polishing efficiency and smoother (0.19 nm Ra) surfaces without generating defects under optimal polishing conditions; thus, this method has potential applications to achieve semiconductor wafer fabrication with a simple polishing setup. © 2019 The Electrochemical Society.