SILICON-NITRIDE OXIDATION BASED ON OXYNITRIDE INTERLAYERS WITH GRADEDSTOICHIOMETRY

The oxidation kinetics of Si3N4 were modeled by describing the simulta neous diffusion and reaction of interstitial oxygen that is believed t o occur inside of the silicon oxynitride interlayer, The oxynitride wa s assumed to have a variable composition, and oxidation was described as a reaction where interstitial oxygen is incorporated into the netwo rk structure of the oxynitride and nitrogen is removed, It was assumed that both the diffusion coefficient and the solubility of interstitia l oxygen decrease as the nitrogen content of the network structure inc reases. The results accurately describe both the formation of an oxyni tride layer during oxidation, and the relatively slow oxidation kineti cs of Si3N4 (compared to Si and SiC).