Characterization of Si(111) surface nitridation on the properties of Si3N4 films grown by RF-N2 plasma exposure

Si
3
N
4
ultra-thin film were grown on nitridation of Si(111) surface by RF-N
2
plasma exposure. We discussed the effect of nitridation time, N2 flow rate and RF power on the optical, chemical, structural properties of Si
3
N
4
ultra-thin film. The surface and interface chemical composition and surface morphology are investigated by using transmission electron microscope (TEM), ellipsometer, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). TEM image shows that RF power of 350 W induced the some damage of Si(111) surface. Also, the thickness of Si
3
N
4
is approximately 5 nm. The binding energy of Si
$2\mathrm{p}_{3/2}$
located at
$101.9 \pm 0.1\ \mathrm{eV}$
are attributed to the Si-N bonds in a Si
3
N
4
compound. Smooth Si
3
N
4
ultra-thin film was obtained at nitridation time nearly to 1hr with RF power of 300 W, which was measured the refractive index (n) nearly to 1.88 at 632 nm. The increase in refractive index with decrease RF plasma exposure time is probably attributed to the chang in stoichiometric of film and surface damage.