We have examined the reactions on Si(100) induced by collision of hyperthermal chlorine or Xe atoms. It is demonstrated that etching reactions are enhanced by kinetic energy of incident atomic and molecular chlorine for the temperature range between 200 and 400°C. The dominant etch products are SiCl₂ for both beams irradiation. The etching rate is dependent on the translational energy of chlorine atoms and molecules. All etching reactions are slightly dependent on the sample temperature, and their activation energies are about 0.2 eV. No etching products was observed from chlorine adsorbed Si(100) surfaces with irradiation of hyperthermal Xe beams (∼5 eV). These results suggest that the enhanced etching reaction follows an Eley-Rideal reaction mechanism where the reaction is mainly driven by the kinetic energy of incident chlorine. However, when the Xe atom beams were impinged on the fluorinated surfaces which were prepared by the exposure of XeF₂, desorption of fluoride (SiF₃ or SiF₄) from the fluorinated layers was observed. After the Xe irradiation, SiF₄ perk disappeared in the temperature-programmed desorption spectra. As a result of collision of Xe atoms, precursor of the thermal desorption of SiF₄ desorbs from the fluorinated surfaces. It is clearly demonstrated that a collision-induced reaction of the fluorinated layer by hyperthermal Xe atoms.