Reliability of ultrathin nitrided oxides grown in low pressure N2O ambient

The influence of N₂O oxynitridation and oxidation pressure on reliability of ultrathin gate oxides from 4 down to 2.5 nm thickness was investigated. A set of different oxidation parameters was applied during oxide growth which comprised oxidation pressure and N₂O partial pressure during rapid thermal oxidation. The reliability of the oxides was tested by constant voltage stress. Evaluation of the resulting times to soft breakdown (t_sbd) for different stress voltages allows to predict a supply (gate) voltage V^10y,max providing an oxide lifetime of 10 years. For this extrapolation, t_sbd was assumed to increase exponentially as stress voltage is reduced. The slope of the extrapolation is found to become steeper as oxides become thinner, which implies higher V^10y,max and thus higher reliability for thinner oxides as under an assumption of a uniform slope for all thicknesses. Further, the results of this extrapolation demonstrate that oxidation in N₂O containing ambient can improve oxide reliability for ultrathin gate oxides.