Microstructural characterization of stoichiometric buried Si 3N 4 films

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 113; no. 1; pp. 227 - 230
• Main Authors: Paloura, E.C., Ginoudi, A., Markwitz, A., Lioutas, Ch, Katsikini, M., Bethge, K., Aminpirooz, S., Rossner, H., Holub-Krappe, E., Zorba, T., Siapkas, D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1996
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/0168-583X(95)01367-9

The properties of buried stoichiometric Si 3N 4 layers are studied using Extended X-ray Absorption Fine Structure (EXAFS), Near-Edge X-ray Absorption Fine Structure (NEXAFS), Infrared Absorption (IR), Nuclear Reaction Analysis (NRA) and Cross-Section Transmission Electron Microscopy (XTEM). The samples were fabricated with ion-implantation using 200 keV 15N ions and a fluency of 1.4 × 10 18 at./cm 2 and they were characterized in the as-grown state and after annealing. The N Si ratio, measured with NRA, is 1.33, which corresponds to stoichiometric nitrides. Analysis of the EXAFS spectra measured at the N-K-edge indicate that the samples are stoichiometric to a microscopic scale, i.e. the bond lengths and coordination numbers in the 1st and 2nd nearest-neighbor shells are identical to those of a stoichiometric nitride. After annealing at 1200°C for 2 h the α-Si 3N 4 phase is formed, as detected by IR absorption measurements, while the small concentration of N-dangling bonds, present in the as-implanted state, are completely annealed out, as indicated by the NEXAFS spectra. However, the EXAFS results do not indicate any change in the microstructure of the film. Finally, TEM observations confirm the formation of a nitride layer and reveal the presence of a heavily damaged region in the back interface with the underlying Si layer.