N AND AR ION-IMPLANTATION EFFECTS IN SIO2-FILMS ON SI SINGLE-CRYSTAL SUBSTRATES

The chemistry of an argon-ion-irradiated interface between an amorphous silicon dioxide film and a silicon single-crystal substrate was studied by determining the kind and depth distribution of compounds formed after nitrogen implantation at a depth more shallow than the SiO2 film thickness. With this study we intended to obtain some insight into the chemical and physical processes involved in the formation of silicon oxynitrides in silica as a consequence of nitrogen ion implantations. Samples were mainly characterized by x-ray photoelectron and Fourier-transform infrared spectroscopies. Scanning electron microscopy, Rutherford backscattering spectrometry, nuclear reaction analysis, and secondary-ion mass spectrometry techniques were also used to complete the set of results. The experimental evidences are consistent with a picture of an argon-induced radiation damage in terms of Si-O and Si-Si bond breaking in the SiO2 and in the silicon substrate regions, respectively. The subsequently implanted nitrogen atoms are drawn toward the interface by a chemical driving force, and there interact with unsaturated silicon bonds to produce SiOxNy or SiN(z) compounds. The formation of a large amount of these compounds at the interface is responsible for very rough surface morphological features.