SIMS AND AES CHARACTERIZATION OF ULTRATHIN NITROXIDE DIELECTRIC LAYERS ON SILICON PREPARED BY N2O-RTP

Ultrathin oxides prepared by rapid thermal oxidation in N2O in the tem perature range from 800-degrees-C to 1200-degrees-C have been investig ated by SIMS and AES. The accumulation of nitrogen in the region close to the interface has been analysed with high depth resolution and ove r three orders of magnitude of concentration. The effective activation energy for the nitrogen accumulation has been estimated to be 0.6 eV in the high temperature region and 2.4 eV at lower temperatures and fo r preoxidized wafers. The maximum nitrogen concentration of 4 at.% was found inside the oxide layer at a distance of 0.5-1.5 nm from the oxi de/silicon interface. After formation of this nitrogen-enriched layer, this interlayer moves during further oxidation with the same velocity as the oxidation front, without significantly changing its effective thickness and position relative to the interface.