Crystalline Silicon Nitride Films on Si(111): Growth Mechanism, Surface Structure and Chemistry down to Atomic Scale

A detailed investigation of the growth mechanism of ultra-thin silicon nitride (Si3N4) films on Si(111) substrates, their structure, morphology and surface chemistry down to atomic scale have been investigated using various surface analytical techniques such as low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and ESCA microscopy. A radio frequency N2 plasma source from Epi Uni-bulb has been used for the nitridation of atomically clean Si(111) surfaces. The substrate temperatures during the nitridation process were ranging from 600–1050°C and the plasma exposure times were varied from 5 s for initial nucleation up to 45 min for saturation thickness. The initial stage of N nucleation on Si(111), how the structure and morphology of the nitride films depend on thickness and temperature, surface atomic reconstructions and the nitride film chemical composition are discussed here. All findings are explained in terms of thermally activated inter-diffusion of Si and N atoms as well as the surface adatom diffusion/ mobility.