Characterization of ultra thin oxynitrides: A general approach

The determination of nitrogen depth profiles in thin oxynitride layers (1.5-3 nm) becomes more and more important in microelectronics. The goal of this paper is to investigate a methodology for the characterization of thin oxynitride layers with the aim to establish in a quantitative manner the layer thickness, N-content and detailed N-depth profile. For this study ultra thin oxynitride films of 2.5 nm on Si were grown by oxygen O2 annealing of Si followed by a NO annealing. The global film characteristics were measured using spectroscopic ellipsometry (SE) (thickness), atomic force microscopy (AFM) for roughness and X-ray photoelectron spectroscopy (XPS) for total O- and N-content. Depth profiles of oxygen, silicon and nitrogen were obtained using (low energy) secondary ion mass spectroscopy (SIMS) and time of flight (TOF)-SIMS, high resolution-Rutherford backscattering (H-RBS) (magnetic sector and TOF) and high resolution-elastic recoil detection (H-ERD). A comparison of the results obtained with the different techniques is presented and discussed