The effect of coincident atomic hydrogen on the gas-source molecular beam epitaxial growth of silicon from disilane

Abstract

The interaction of atomic hydrogen with both the clean Si(1 0 0) surface, and this same surface under conditions leading to steady-state epitaxial growth of Si from the reaction of disilane, Si 2H 6, has been examined. Reflectance anisotropy spectroscopy has been employed to measure the hydrogen adatom coverage on vicinal Si(1 0 0) surfaces as a function of atomic hydrogen exposure at differing substrate temperatures and differing atomic hydrogen fluxes. This set of experimental data can be fit well by a “hot-precursor” model that includes the elementary steps of adsorption, abstraction, migration, and desorption of atomic hydrogen, and where we account explicitly for adsorption site occupancy. Reflection high-energy electron diffraction has been used to quantify the effect of atomic hydrogen on the gas-source molecular beam epitaxial growth of Si from Si 2H 6. We observe suppression of the epitaxial growth rate by atomic hydrogen 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 Si 2H 6, the adsorption of atomic hydrogen, and the recombinative desorption of molecular hydrogen from the Si(1 0 0) surface.