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-10 y,V-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-10 y,V-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. (C) 2001 Elsevier Science Ltd. All rights reserved.