Effectiveness of plasma nitrided silicon oxynitride as a barrier layer between high k materials and Si substrates

In this work, low temperature (300 - 450°C) plasma nitridation was conducted using N₂O and NH₃ atmosphere to produce an ultrathin SiO_xN_y layer. The bonding structure, distribution, and quantity of nitrogen and their effects on the growth kinetic of SiO_xN_y layers are studied by X-ray photoelectron spectroscopy (XPS). It is found that nitrogen atoms pile at the SiO_xN_y/Si interface at the very beginning of plasma N₂O and NH₃ nitridation. Due to the lack of additional Si source and low diffusivity of O or N atoms at low temperature, plasma nitridation will form a self-limited growth of SiO_xN_y layer. Thermal stability of the interlayer between ultrathin Ta₂O₅films on bare Si, plasma N₂O nitrided Si, and plasma NH₃ nitrided Si is also studied.