An efficient approach for atomic-scale polishing of single-crystal silicon via plasma-based atom-selective etching

To realize the damage-free, highly efficient, and atomic-level polishing of single-crystal Si, plasma-based atom-selective etching (PASE) is proposed in this study as a generic polishing approach for Si wafers. The polishing effect of PASE is realized through the selective removal of Si atoms with more dangling bonds under high temperature. Plasma diagnostics are carried out to investigate the radical composition, the density of plasma, and the etching temperature. The key parameters of PASE are optimized, and the PASE of Si (100) with a material removal rate greater than 0.7 mu m/min was realized. A ground Si (100) surface can be quickly smoothed by PASE, with the Sa roughness being reduced from 195 nm to below 1.0 nm within 5 min, and the polished surface is proven to be crystallographically perfect. The PASE of (110)- and (111)-oriented Si wafers is also proven effective, demonstrating that PASE is a generic polishing approach for Si regardless of orientation. The entire surface flattening of a 2-inch Si wafer was carried out by numerically controlled PASE, and the wafer flatness was reduced from 37.29 mu m to 4.92 mu m through optimized scanning conditions. Overall, this study has shown that PASE is a promising approach for high-efficiency and high-quality polishing of Si.