Incorporation of N into Si/SiO2 interfaces: Molecular orbital calculationsto evaluate interface strain and heat of reaction

The determining factor for the accumulation of N at a Si/SiO2 interface dur ing oxynitridation of the interface was investigated using a quantum-chemic al method. Both mechanical and chemical factors (the interface strains and the heats of reaction of the oxynitridation) were considered. Though a slig ht relaxation of interface strain occurs when the interface has a certain t ype of oxygen-vacancy defect, we found the N incorporation does not relax t he interface strain in most cases. The exothermicity and endothermicity of the oxynitridation reaction in the Si and SiO2 films, respectively, are the primary cause of the accumulation of N at the interface. (C) 1999 American Institute of Physics. [S0003-6951(99)02831-4].