Growth of Silicon Nitride on Silicon by Electron Cyclotron Resonance Plasma Nitridation

In this work we report the formation of silicon nitride films on silicon substrates by N₂ Electron Cyclotron Resonance plasma nitridation. An absorption band located around 860-890 cm^-1 was observed in the infrared spectra, which is slightly above the wave number of the characteristic silicon nitride band. According to ellipsometry measurements performed at lambda= 532 nm, the thickness of the films ranged from 1.2 nm to 3.6 nm for nitridation times between 0.5 min. and 60 min. An empirical exponential law for the thickness as a function of nitridation time was found. The obtained refractive index values were higher than the expected for stoichiometric silicon nitride, which indicates that the films may be slightly silicon rich. Cross section transmission electron microscopy showed the formation of a thin layer on top of the silicon with thickness consistent with the values obtained by ellipsometry. Energy dispersive X-ray analysis confirmed the presence of N in this layer.