Study of thermal stability of CVD Ta2O5/Si interface

The effects of vacuum and inert gas annealing of ultra-thin (20 Angstrom) CVD Ta2O5 films deposited on Si substrates, with and without oxynitride interface layer, on the Ta2O5/Si interface stability were examined extensively by means of in-situ X-ray Photoelectron Spectroscopy (XPS), ex-situ Time-of-Flight Secondary Ion mass Spectrometry (ToF-SIMS), and Temperature Programmed Reaction(TPR). When annealed to 680 degrees C for up to 50 min, changes in similar to 20 Angstrom Ta2O5 films formed on Si(100) are negligible, but annealing to 820 degrees C for 10 min in vacuum, Ar or N-2 produces major chemical restructuring. SiO is formed at the Ta2O5 - Si(100) interfaces and becomes incorporated into the tantalum oxide. A reduced form of Ta, attributed to TaSiX, forms at the buried interface. Extending the annealing time to 20 min produces no further changes. SiO desorbs during annealing at 1000 degrees C. Nitriding Si prior to forming the Ta2O5 film deposition inhibits these processes.