Controlled fabrication of Si nanocrystals embedded in thin SiON layers by PPECVDfollowed by oxidizing annealing

Abstract

The controlled fabrication of Si nanocrystals embedded in thin silicon oxynitride films (<15 nm) on top of a silicon substrate has been realized by PPECVD withN2O–SiH4 precursors. The effect of inert and oxidizing annealing processes on the Si nanocrystalspatial and size distributions is studied by coupling ellipsometry measurements andcross-sectional transmission electron microscopy observations. This study gives aninteresting insight into the physics underlying the Si nanocrystal nucleation, growth andoxidation mechanisms. In particular, it evidences the presence in the as-deposited films of ahigh density of small amorphous Si particles that crystallize after high temperature thermalannealing. Annealing under oxidizing conditions is shown to be a powerful way to createtunnel oxides of good quality and controlled thickness needed to design future memorydevices.