A study of the growth kinetics of SiO₂ in N₂O(for MOSFETs)

The results of thermal oxidation studies in N₂O on P (100) silicon substrates having initial dry oxygen oxide thicknesses of up to 145 A, indicate that the growth characteristics of ultra-thin SiO₂ films show no signs of dielectric thickness saturation. For total dielectric thicknesses as large as 160 λ, N₂O oxidation rate is generally linear, and significantly smaller than the corresponding rate in dry oxygen. This linear regime has been modeled by a linear rate constant with an activation energy of 1.0 eV. Prior to the linear regime, a short accelerated growth phase has been observed. As the initial oxide thickness on the substrate is increased, the results indicate that the initial accelerated growth characteristics become less and less pronounced. An empirical model, based on the gradual accumulation of rate retarding nitrogen species at the Si/SiO₂ interface, has been developed and added to a modified accelerated growth rate model, to successfully simulate this phase. The results are consistent with AES data which show that the higher the initial oxide thickness on the substrates, the greater the nitrogen peak concentration at the Si/SiO₂ interface for a given N₂O exposure time.