COLLISIONAL AND CHEMICALLY GUIDED PROCESSES IN LOW-ENERGY ION-BEAM OXIDATION

It has been shown [Todorov and Fossum, J Vac Sci Technol, B6, 466 (1988)] that ultra-thin (d-almost-equal-to 50-angstrom) oxide films can be grown on silicon surfaces at reduced substrate temperatures using oxygen-containing low energy ion beams (E < 200 eV). The oxide film evolution with increasing fluence can be explained by a general model based on the competing processes of oxygen incorporation and sputtering. The delivery of the oxidizing species to the lower interface of the growing film is by means of implantation and radiation-enhanced diffusion. It is demonstrated that the ion range distributions calculated on the basis of ballistic atomic transport are insufficient to explain the experimental data. Analytical calculations and dynamic computer simulation are used to investigate the role of ballistic and chemically guided atomic transport and to assess the importance of radiation-enhanced mobility and reactivity.