Evidence that N₂O is a Stronger Oxidizing Agent than O₂ for the Post-Deposition Annealing of Ta₂O₅ on Si Capacitors

Cross-sectional transmission electron microscopy (XTEM), secondary ion mass spectrometry (SIMS) and capacitance measurements were used to study the effect of post-deposition annealing on Ta 2 O 5 /Si structures. A significantly thicker SiO x interfacial layer was formed at the Ta 2 O 5 /Si interface, if N 2 O was used instead of O 2 for post-deposition annealing. This indicates that N 2 O is a stronger oxidizing agent than O 2 . It is known that the leakage current of Ta 2 O 5 capacitors is greatly reduced if N 2 O is used instead of O 2 for post-deposition annealing. This may also be partially explained by postulating that N 2 O annealing is more effective in the suppression of oxygen vacancies. Furthermore, the suppression of Si diffusion from the Si substrate into Ta 2 O 5 due to the thicker SiO x interfacial layer can be another factor. The basic reason for the superiority of N 2 O is that the energy required to produce free O atoms is lower than that for O 2 . From this point of view, we can also predict that the use of NO will be worse than that of O 2 because the energy required to produce free O atoms is higher than that of O 2 .