Comparison of defect structure in N₂O- and NH ₃-nitrided oxide dielectrics

Electron spin resonance spectroscopy is used to identify and compare point defects in N₂O-nitrided, NH₃-nitrided, and conventional SiO₂ films. We detect only three types of defects in these dielectrics. P_b centers, the primary source of interface states in Si/SiO₂ systems under all technologically significant circumstances, appear in all three dielectrics. Both N₂O and NH₃ nitridation result in higher as-processed P_b interface defect densities, but lower radiation-induced P_b defect generation. Thus N₂O nitridation appears capable, as does NH₃ nitridation, of providing reduced radiation-induced interface state generation. In addition, both nitridations appear capable of lowering the number of radiation-induced E' centers, the dominant hole trap in conventional thermal oxides. NH₃ nitridation, however, appears to offer greater resistance to radiation-induced generation of these traps. NH₃ nitridation also results in a large number of bridging nitrogen centers, and strong evidence indicates that the bridging nitrogen centers are the dominant electron trap in NH ₃-nitrided and -reoxidized nitrided oxide films. These defects are absent in N₂O-nitrided films, which are known to exhibit reduced levels of electron trapping.