Reliability of ultrathin nitrided oxides grown in low pressure N2O ambient

The influence of N2O oxynitridation and oxidation pressure on reliability o f ultrathin gate oxides from 4 down to 2.5 nm thickness was investigated. A set of different oxidation parameters was applied during oxide growth whic h comprised oxidation pressure and N2O partial pressure during rapid therma l oxidation. The reliability of the oxides was tested by constant voltage s tress. Evaluation of the resulting times to soft breakdown (t(sbd)) for dif ferent stress voltages allows to predict a supply (gate) voltage V-10 y,V-m ax providing an oxide lifetime of 10 years. For this extrapolation, t(sbd) was assumed to increase exponentially as stress voltage is reduced. The slo pe 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. Furt her. the results of this extrapolation demonstrate that oxidation in N2O co ntaining ambient can improve oxide reliability for ultrathin gate oxides. ( C) 2001 Elsevier Science Ltd. All rights reserved.