COMPOSITIONAL AND ELECTRICAL-PROPERTIES OF ECR-CVD SILICON OXYNITRIDES

Silicon oxynitride layers were deposited by electron cyclotron resonan ce (ECR) plasma enhanced chemical vapour deposition (PECVD). Oxygen, n itrogen and 5% argon diluted silane were used as precursors. The gas c omposition in the plasma was varied over a wide range to get compositi ons from pure SiO2 to SiOxNy layers with around 20% O content. Large N -2/O-2 flow ratios are required to get significant N concentrations in the SiOxNy deposited layers. Pure Si3N4 layers could only be obtained when O-2 flow was completely suppressed. The infrared spectra of ECR SiO2 are very similar to those of thermally grown oxides, but signific ant differences were found between the ECR and the high-temperature CV D Si3N4 spectra. MOS devices fabricated with these layers show that th e interface state density increases from about 10(11) to 10(12) cm(-2) eV(-1) when the layer composition changes from pure SiO2 to pure Si3N 4.