Characterization of ultra thin oxynitrides: A general approach

The determination of nitrogen depth pro®les 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 pro®le. For this study ultra thin oxynitride ®lms of 2.5 nm on Si were grown by oxygen O2 annealing of Si followed by a NO annealing. The global ®lm characteristics were measured using spectroscopic ellipsometry (SE) (thickness), atomic force microscopy (AFM) for roughness and X-ray photoelectron spectroscopy (XPS) for total Oand N-content. Depth pro®les of oxygen, silicon and nitrogen were obtained using (low energy) secondary ion mass spectroscopy (SIMS) and time of ̄ight (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 di€erent techniques is presented and discussed. Ó 2000 Elsevier Science B.V. All rights reserved.