The influence of annealing (900◦C) of ultra-thin PECVD silicon oxynitride layers

This work reports on changes in the properties of ultra-thin PECVD silicon oxynitride layers after high- temperature treatment. Possible changes in the structure, composition and electrophysical properties were investigated by means of spectroscopic ellipsometry, XPS, SIMS and electrical characterization methods (C-V, I-V and charge- pumping). The XPS measurements show that SiOxNy is the dominant phase in the ultra-thin layer and high-temperature annealing results in further increase of the oxynitride phase up to 70% of the whole layer. Despite comparable thickness, SIMS measurement indicates a densification of the annealed layer, because sputtering time is increased. It suggests complex changes of physical and chemical properties of the investigated layers taking place during high-temperature annealing. The C-V curves of annealed layers exhibit less frequency dispersion, their leakage and charge-pumping currents are lower when compared to those of as-deposited layers, proving improvement in the gate structure trapping properties due to the annealing process.