Nucleation and growth of silicon by CVD

Abstract

Nucleation of silicon on various substrates is shown to depend primarily on a number of kinetic factors that determine the steady state concentration of silicon monomer adatoms on the surface and give rise to a well defined concentration of stable clusters. After coalescence a silicon-on-silicon growth is left where a competition is present between incorporation on monoatomic steps and the formation of additional nuclei on the surface between the steps. After the nucleation state, silicon is grown via CVD in a number of ways aimed at obtaining epitaxial, polycrystalline or amorphous layers. Growth conditions are reviewed, including growth under atmospheric pressure and reduced pressures, in a cold-wall or a hot-wall reactor and under various thermodynamic conditions of supersaturation. It is concluded that nucleation and growth at higher temperatures are relatively well understood. Growth at lower temperatures, which is of increasing technological importance, is dependent on kinetic factors specific to each combination of reactant, substrate and ambient.