Reliability of ultra-thin gate oxides grown in low-pressure N2O ambient oron nitrogen-implanted silicon

The influence of nitrogen incorporated at the gate oxide interface on the r eliability and electrical behavior of MOS capacitors was investigated. Inco rporation of nitrogen was accomplished either by either rapid thermal oxida tion (RTO) in N2O or N2O/O-2 atmosphere at pressures between 75 to 500 mbar or by implantation of nitrogen at 20 keV and doses between 10(13) to 10(15 ) cm(-2) into the substrate prior to RTO. Characterization of MOS capacitor s with oxide thicknesses between 2.9 to 3.9 nm was achieved by reliability measurements at constant current or constant voltage stress, respectively. These measurements were correlated to the nitrogen dose at the gate interfa ce which was determined by SIMS analysis. Stress reliability showed a sensi tive dependence on the processing conditions. An accurate adjustment of the nitrogen dose at the gate interface is mandatory to attain improved reliab ility of nitrided oxides.