To develop 32 nm node devices, the degradation of atomic layers on the surface of Si substrates must be controlled! During the etching of a SiO2 or Si3N4 hard mask or sidewall, the surface of Si is attended due to exposure to fluorocarbon plasma. The authors have quantitatively evaluated the relationship between the energy of incident ions and the thickness of the fluorocarbon polymer for a CH2F2/CF4/Ar/O-2 plasma in a dual frequency CCP system. At a fixed ion energy the thickness of the damage layer (T-d) basically depended on the thickness of the fluorocarbon polymer (TC-F). When the TC-F was changed by controlling the O/CFx gas ratio, T-d had a minimum thickness under the conditions at balance point: P-b, under which the TC-F was nearly equal to ion penetration depth: D-p. Using molecular dynamics simulation, reaction around the transition from SiO2 to Si was clarified. The damage was done to the Si before the SiO2 was completely removed, and the largest T-d was observed when the SiO2 was etched off. After that, TC-F began to increase because there was no longer an outflux of O from SiO2 and the damage decreased as the unstable SiFx species in the damaged layer desorbed. Once the TC-F became thicker than the ion penetration depth, the damaged layer got buried and T-d stopped changing. When the ion penetration depth was controlled to be equal to TC-F in a steady state under low ion energy conditions, the T-d was reduced to less than 1 nm. (c) 2007 American Vacuum Society.