High resolution depth profiling in silicon oxynitride films using narrow nuclear reaction resonances

Abstract

We report here on the determination of depth profiles of oxygen and nitrogen with nanometer resolution in silicon oxynitride films with thicknesses below 3 nm. We have studied oxynitride films grown by rapid thermal processing of Si (0 0 1) wafers in various Nitric Oxide (NO) atmospheres. Angle Resolved X-Ray Photoelectron Spectroscopy (ARXPS) analyses were carried out to determine the chemical composition of the films as well as the spatial distribution of the chemical bonds. The nuclear depth profiling method uses narrow, isolated resonances found in the cross section of the nuclear reactions 18O(p,α) 15N at 152 keV and 15N(p,αγ) 12C at 429 keV. The excitation curves of the nuclear reactions in the neighbourhood of the resonance energies can be used to determine the concentration versus depth profiles by means of SPACES, a personal computer implementation of the stochastic theory of energy loss. We discuss aspects of the simulation of excitation curves and the effect of NO pressure on the structure of the oxynitride film.