High-resolution transmission electron microscopy was used to show that the atomic structures at a Si3N4/Si interface were clearly different from those at a SiO2/Si interface. By using first-principles calculations it was also found that, in one of the observed N-induced interfacial geometries, a dangling bond was produced on a Si atom adjacent to a N atom. It was therefore argued that such N-induced interfacial dangling bonds could cause degradation in the performance of metal–oxide–semiconductor transistors with Si–oxynitride (SiON) gate dielectrics when the N concentration was increased at the SiON/Si interfaces. It was also argued that the difference in flatness between Si3N4 and SiON/Si interfaces and SiO2/Si interfaces was the result of the differences between their atomic structures.

Atomic Structures at a Si–Nitride/Si(001) Interface. N.Ikarashi, K.Watanabe, Y.Miyamoto: Journal of Applied Physics, 2001, 90[6], 2683-8