The mechanisms and the characteristics of a pyrolytic process of halogen-containing gases are investigated theoretically and experimentally. A calculation method of analyzing chemical reactions on solid surfaces is proposed. The dissociation process of Cl2 and SF6 gas moleculeon a Si (100) surface is investigated by calculating the local energy of the molecule, and a model of the pyrolytic process is proposed. It is confirmed that the dissociation energy of the molecule decreases due to a specific process on the solid surface which can not operate on the oxidized Si surface, and that the dissociation process of CF4 gas molecule is promoted by oxygen gas molecule.
