Kinetic studies of growth of silicon and silicon germanium thin films: Gas-surface reactivity, germanium surface segregation, and the effect of coincident atomic hydrogen

The reaction probabilities, SR, of GeH4 and Ge 2H6 on clean Si(100) and on Ge- and/or H-covered Si(100) surface have been measured employing supersonic molecular beam scattering technique. Kinetic models, which are based on the experimental data, were proposed to understand the mechanisms of the dissociative adsorption reactions of GeH4 and Ge2H6 on Si(100) surface and the mechanism of the acceleration of hydrogen desorption by the addition of Ge. Surface reactivity of Si1-xGex alloys grown on Si(111) surface was quantified using the same technique. Surface structures were found to play an important role in determining surface reactivity. Two in situ surface probes, namely x-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectrometry (LEISS), were employed to quantify Ge surface segregation during the growth of Si1-xGe x alloy thin films on both Si(100) and Si(111) surfaces. Ge enrichment in the subsurface was observed, and it can be explained quantitatively by a statistical thermodynamic model.; The interaction of atomic hydrogen with both the clean Si(100) surface, and this same surface under conditions leading to steady-state epitaxial growth of Si from the reaction of disilane, Si2H6, has been examined, employing both reflectance anisotropy spectroscopy (RAS) and reflection high-energy electron diffraction (RHEED). The suppression of the epitaxial growth rate by atomic hydrogen was observed under a variety of reaction conditions. This set of data are described well by a model that combines rate expressions for the dissociative adsorption of Si2H6, the adsorption of atomic hydrogen, and the recombinative desorption of molecular hydrogen from the Si(100) surface. The etch rates of Ge overlayer and Si by atomic hydrogen under a variety of experimental conditions were quantified employing XPS and LEISS. The presence of dihydride species was found to be essential for the etching reactions. A kinetic model was proposed to understand the experimental data.; Based on the kinetic studies presented in this thesis, a novel process was proposed to achieve selective epitaxial growth of Si and Si1-x Gex. Preliminary results show that up to 300 nm epitaxial silicon has been grown while with no sign of polycrystalline silicon growth.