IR ELLIPSOMETRY INVESTIGATIONS OF N2O-NITRIDED SILICON-OXIDE THIN-FILMS ON SILICON

Thin SiO2 films are treated by rapid thermal processing in N2O gas and characterized by spectroscopic IR ellipsometry. In the longitudinal o ptical mode, Si3N4 can be separated from SiO2 as a result of the diffe rent properties of the reststrahlen bands. Experimental results are di scussed and compared with results from secondary-ion mass spectrometry and etching investigations. One can find that nitrogen is preferentia lly located at the interface and influences the etching behaviour. By means of IR ellipsometry the detection of Si3N, is possible as a contr ibution to the SiO2 layer up to a volume fraction of 5% when this cont ent is considered by the effective-medium approximation.