Composition of Ta 2O 5 stacked films on N 2O- and NH 3-nitrided Si

Abstract

The composition and microstructure of rf sputtered 20 nm Ta 2O 5 on N 2O or NH 3 Rapid Thermal Nitrided (RTN) Si substrates have been investigated by X-ray photoelectron spectroscopy. RTN at 800 and 850 °C is effective to suppress active oxidation of Si. There is no evidence for the presence of SiO 2 at Si interface. A lightly nitrided surface is established in both cases without a formation of detectable oxynitride layer at Si. A layered nature of the films is observed, with stoichiometric tantalum pentoxide at and close to the films’ surface. In the depth, the films are mixed ones whose composition depends on the nitridation ambient. N 2O treatment stimulates oxidation processes during the film deposition while NH 3 nitridation results to a less effective oxidation and produces Ta-silicate like film. The correlation between the composition of the interfacial regions and the nitridation gas is also discussed. The results suggest that hydrogen, as a component of nitridation ambient, plays significant role in the reactions controlling the exact composition of the deposited Ta 2O 5, activating reactions with nitrogen. Nitrogen related reactions likely occur with NH 3 processing but do not with N 2O one. The presence of nitrogen feature is not detected in N 2O-samples spectra at all. In the integration perspective, preliminary RTN of Si in N 2O or NH 3 could be a suitable way to produce layered Ta 2O 5-based films with more or less presence of tantalum silicate with a trace of nitrogen, either only at the interface with Si (N 2O-process) or in the whole film (NH 3-process).