Electrical characterisation of thin silicon oxynitride films deposited by low pressure chemical vapour deposition

Dielectric properties of various silicon oxynitride thin films (similar to 30 nm), deposited by low pressure chemical vapour deposition (LPCVD) technique, are studied by capacitance-voltage (C-V), current-voltage (I-V) and ageing under constant current injection (V-t). It is found that the nitrogen-rich oxynitride layers have lower mid-gap interface trap sheet densities, lower fixed charge sheet densities and higher breakdown fields in comparison to oxygen-rich oxynitride layers. The experimental data for the dielectric constant are compared to the Bruggeman theory applied to the mix of silicon dioxide SiO2 and silicon nitride Si3N4 A good agreement is obtained except for the oxygen-rich silicon oxynitride films where the SiOxNy porous structure and leakage current are responsible for errors. A Poole-Frenkel thermal-emission is shown to be the dominant conduction mechanism in the silicon oxynitride films while the leakage-current increases with increasing O/Si ratio. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.