Interlayer growth and electrical behavior of Ta2O5/SiOxNy/Si gate stacks

Abstract

Growth and reaction of the interlayer (IL) between ultrathin Ta2O5 films and bare, and N2O or NH3 plasma-nitrided Si substrate, before and after rapid thermal oxidation (RTO), is examined by X-ray photoelectron spectroscopy. The IL thickness extracted from the attenuated Si 2p photoelectron signal shows that the thermal instability between Ta2O5 and Si causes the IL to grow further after RTO annealing. The SiOxNy layer formed on the N2O plasma-nitrided Si appears to provide better barrier efficiency in retarding the growth of IL. For current-voltage measurements, an anomalous saturated current is observed for as-deposited Ta2O5 films when stressed positive bias, presumably due to the film/substrate stress-induced Si bandgap widening. After RTO annealing, the leakage current through Ta2O5/IL stacks is higher under positive bias than under negative bias. Ta2O5 deposited on N2O-nitrided Si also exhibits the best leakage behavior among the three systems with the current of 1.7 x 10(-8) A/cm(2) at E = 2.0 MV/cm and 1.9 x 10(-7) A/cm(2) at E = +2.0 MV/cm. The correlation between leakage current as well as IL growth is also discussed. (C) 2004 The Electrochemical Society.