A study of silicon oxidation and nitridation using surface infrared spectroscopy

Silicon is used in microelectronics in large part because of the unique properties of both SiO₂ and the Si/SiO₂ interface. The properties of SiO₂ have been studied for decades because of its critical importance in devices. In this thesis, the oxidation of silicon, in particular the mechanism and kinetics of basic atomic and molecular processes, is examined from a fundamental perspective.; First, a systematic study was performed on the “dry” oxidation of the hydrogen terminated H/Si(111) and H/Si(100) surfaces by molecular O ₂. The kinetics of the reaction was introduced with a simple model. The effective activation energy per Si-H species for oxygen incorporation was found to be 160 kJ/mol (1.7 eV) for the flat Si(111) surface, and slightly less (1.6eV) for steps. By comparing the H/Si(100) with H/Si(111) surfaces, we have found that the activation energies depend on the hydride species (e.g. di- or mono-hydrides), and within each species, rate variations appear to depend primarily on O₂ access to the Si-SiH backbonds rather than strain associated with surface reconstruction.; The activation energy for “wet” H₂O oxidation of H-terminated Si(111) is ∼150 kJ/mol, ∼10 kJ/mol lower than O ₂ oxidation. We also found that ambient air is much more reactive than either pure H₂O or O₂, implying that impurities (e.g. radicals, hydrocarbons…) present at low concentration are likely causing the high ambient reactivity of the otherwise passive Si-H layer.; New and interesting results were also observed on the oxidation of the clean Si(100)2x1 surface by O₂ at 173K in UHV. A new feature at 1220 cm−1 was assigned as an Si=O mode, the first observation of the silanone group on a silicon surface. Exposure of the oxidized surface to atomic H results in new oxidized dihydride vibrational features. Finally, the reaction between the Si(100)2x1 surface and NH₃ and NO have been studied. NH3 forms a H-Si-Si-NH2 structure after dosing. NO adsorbs on the surface dissociatively forming a surface oxynitride with separate Si-O and Si-N bonds. After annealing to high temperature, 0 leaves the surface as SiO.