Asymmetric etching profile control during high aspect ratio Plasma etch

Abstract

Dependency of asymmetric etched profiles on open-ratio and pattern-size within the wafer was studied in a magnetic Very High Frequency (VHF) Plasma etching system for high aspect-ratio multiple alternating layers of silicon oxide/polysilicon (OP) etching. The etched physical features are sensitive to the overall open ratio on the wafer; the profile sidewalls became bent while the open ratio changed from 8% to 40%. In this study, the profile recovery from a method of design of experiments (DOE) and specific inductively magnetic field applied in the etching system was explored. The resulting etched profile is successfully back to normal on multi-layered OP film stack at 40% of open ratio. Even at next generation node development, the etching based on DOE also demonstrates good shape control on the etched profile which stacked with OP pairs over 3um in thickness in extremely high aspect ratio trench etching.