Interface properties of SiO(x)N(y) layer on Si prepared by atmospheric-pressure plasma oxidation-nitridation

SiO(x)N(y) films with a low nitrogen concentration (< 4%) have been prepared on Si substrates at 400°C by atmospheric-pressure plasma oxidation-nitridation process using O(2) and N(2) as gaseous precursors diluted in He. Interface properties of SiO(x)N(y) films have been investigated by analyzing high-frequency and quasistatic capacitance-voltage characteristics of metal-oxide-semiconductor capacitors. It is found that addition of N into the oxide increases both interface state density (D(it)) and positive fixed charge density (Q(f)). After forming gas anneal, D(it) decreases largely with decreasing N(2)/O(2) flow ratio from 1 to 0.01 while the change of Q(f) is insignificant. These results suggest that low N(2)/O(2) flow ratio is a key parameter to achieve a low D(it) and relatively high Q(f), which is effective for field effect passivation of n-type Si surfaces.