Calculation of energy barriers for the chlorine etching of Si(100) surfacewith step edges

Calculations were carried out to determine energies and barriers involved i n the chlorination process of Si(100) (2 x 1) surfaces and in the subsequen t desorption of Si-containing species. First and second chlorination steps for Si atoms located at step edge sites were investigated. Energy calculati ons for exposed terraces include extremely low and high surface Cl concentr ations. No energy barriers were found for the first chlorination step, whic h also displayed little or no dependence on the surface chlorine concentrat ion. However, the second chlorination step (leading to the formation of an attached -SiCl2 unit) involves a barrier, and calculated energetics depend on the Cl concentration of the terraces. One of the important outcomes of t his study is related to the composition and the structure of the exposed su rfaces. Results strongly indicate that the role played by surface defects a nd by the attached Cl concentration (in the vicinity of the adsorption site s) on reaction energetics is significant. They influence local reactions an d, in turn, affect the overall etching process. (C) 2000 Elsevier Science B .V. All rights reserved.