Plasma-assisted chemical vapor deposited silicon oxynitride as an alternative material for gate dielectric in MOS devices

Silicon oxynitride films have been deposited on Si substrates at 200 °C by a remote-plasma-assisted process in a RF-plasma CVD reactor using Si(OC₂H₅)₄ (TEOS) as a precursor and nitrogen as gas ambient. During deposition the Si substrates were biased with negative voltages of −120 and −600 V or were under no DC bias and the influence of this voltage on the film properties has been considered. Film parameters, such as density, chemical bonds, refractive index, composition, oxide and interface charge densities of the deposited dielectric films have been estimated by analysis of the results from the infrared (IR) spectroscopy, spectral ellipsometry (SE) and capacitance-voltage (C-V) measurements. The IR and SE results have proven the films are oxynitrides of silicon with predominantly oxide network. The analysis of the capacitance-voltage characteristics has shown that the dielectric charge densities increase with increasing DC bias but they remain considerably low in comparison to that for a standard SiO₂/Si structure before any annealing steps.