Atomic structures at a Si-nitride/Si(001) interface

We used high-resolution transmission electron microscopy to show that the a tomic structures at a Si3N4/Si interface are clearly different from those a t a SiO2/Si interface. Using first-principles calculations, we also found t hat, in one of the observed N-induced interfacial geometries, a dangling bo nd was produced on a Si atom adjacent to a N atom. We thus argue that such N-induced interfacial dangling bonds can cause degradation in the performan ce of metal-oxide-semiconductor transistors with Si-oxynitride (SiON) gate dielectrics when the N concentration is increased at the SiON/Si interfaces . We also argue that the difference in flatness between Si3N4 and SiON/Si i nterfaces and SiO2/Si interfaces is the result of the difference between th eir atomic structures. (C) 2001 American Institute of Physics.