Plasma dry etching has been extensively employed in semiconductor manufacturing processes for anisotropic pattern transfer. With device miniaturization, the conventional approach utilizing continuous wave plasma etching does not meet the requirement for sub-nanometer processing nodes, including profile control and atomic-scale etching selectivity. Additionally, the direct plasma exposure of a substrate raises the concern of plasma damage and undesired material removal. We describe improvements of plasma-based etching techniques and identified novel ways for enabling material removal. We have systematically studied different precursor chemistries for atomic layer etching on etching selectivity of SiO2 to Si3N4 and SiO2 to Si and obtained an understanding of the surface chemistry evolution. Compared to the conventional approach that mixes fluorocarbon and hydrogen precursors, selected hydrofluorocarbon can deliver optimal plasma chemistry that produces a reduced F/C film in the deposition step and realizes atomic-scale etching selectivity. We also report a new approach for establishing etching selectivity of HfO2 over Si by integrating substrate-selective deposition into an atomic layer etching sequence. The optimal precursor chemistry can selectively deposit on the Si surface as a passivation layer and convert HfO2 to metal-organic compounds for desorption. Finally, we designed and built a system that consists of an electron flood gun and a remote plasma source to demonstrate the concept of a new etching approach by exploiting electron-neutral synergistic effects. This configuration achieves precisely controlled SiO2 or Si3N4 etching by co-introducing an electron beam and Ar/CF4/O2 remote plasma. This approach also addresses the issue of limited precursor chemistries in electron beam-induced etching.