AES INVESTIGATION OF THE CHEMICAL-STRUCTURE OF SILICON OXYNITRIDE FILMS

The silicon-L//2//,//3VV, nitrogen-KVV, and oxygen-KVV Auger signals have been measured for a series of chemical-vapor-deposited silicon nitride films in which the oxygen content varied from 2 to 67 at. %. Uncorrected derivative spectra and background-corrected, loss-deconvoluted integral lines for silicon nitride films, for clean Si, and for SiO//2 were compared. The silicon spectra indicate that a high-energy Si-L//2//,//3VV feature from the nitride, previously identified with elementally bound Si, actually indicates an oxygen impurity. The N-KVV lineshape is found to be insensitive to oxygen incorporation while the three-peaked oxygen line becomes broader with increasing oxygen content. The valence-electron distribution width in the nitride is more than twice that of the distribution in elemental Si, but the width does not change appreciably with changing oxygen content. These Auger data indicate that oxygen incorporation into silicon nitride results in the formation of oxynitrides for APP 1STH 200 ppm of oxygen in the reactor. Beyond this concentration, silicon oxide is largely formed.