Low energy ion beam interactions with silicon: Cleaning, etching, and thin film growth

The cleaning of silicon surfaces by high temperature annealing and the interactions of low energy (10 eV ∼ 5 keV) ion beams with silicon surfaces, including cleaning, etching, and thin film growth, are studied in this dissertation. The surface morphology of the Si(100) surface is susceptible to the annealing conditions. Both annealing temperature and time determine the surface topography. In the cleaning of silicon by low energy Ar+ beam bombardment, synergism is observed between the kinetic energy of the ions used in bombardment and the annealing temperature. Atomically clean and well order crystalline silicon surfaces were obtained by simultaneous heating and energetic particle bombarding. Chemical reactions induced by the low energy ion collisions were observed during bombardment. The graphitic carbon impurity on the silicon was converted into a carbidic form, that is, SiC was formed. Comparing chemical and physical etching processes, implanted reactive species, in contrast with inert species, is the main difference in their etching products. Etching by Cl+ generates more ionic etching products and a higher etching yield than Ar+. The space charge model was used to understand the behavior of implanted Cl. In the study of thin film growth on Si by Ti + irradiation, temperature is the most important parameter, which determines whether a metallic Ti film or a TiSi₂ film is formed. A chemical shift was observed in the Si_2p peak in XPS and applied to characterization of the Ti and TiSi₂ films in depth profiling. The formation of titanium silicide at the interface between the metallic Ti film and the Si substrate was found. A synergism of kinetic energy and temperature was observed in the analysis of their interface. The depth profile XPS study confirmed that the stoichiometry of the silicide film matched that of TiSi ₂.