Compositional characterization of very thin SiO2/Si3N4/SiO2 stacked films by x-ray photoemission spectroscopy and time-of-flight-secondary-ion-mass spectroscopy techniques (original) (raw)
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Japanese Journal of Applied Physics, 1982
The electronic properties of Si–SiO2 interface states in Metal-Nitride-Oxide-Silicon (MNOS) with thick oxide films are investigated. It is shown that a large number of acceptor-like interface states are created when MNOS is annealed at high temperatures, and that subsequent low temperature hydrogen annealing reduces the number of these states. We found that the energy distribution of the interface states is independent of their density. The possible cause of these interface states may be thermal stress induced at the interface.
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Surface Science, 2002
Nitridation of silicon dioxide layers at low temperatures by the use of nitrogen plasma generated by low energy electron impact has been investigated by means of X-ray photoelectron spectroscopy. The nitrogen concentration is increased by the application of a negative bias voltage to the specimen, indicating that N þ ions are the reacting species. When nitridation is performed above 450°C, only one peak is observed at 397.9 eV, and it is attributed to N(-Si) 3 (nitrogen atom bound to three Si atoms). For the nitridation below 400°C, on the other hand, a peak appears at 399.2 eV in addition to the 397.9 eV-peak. When the film nitrided at 400°C is heated at 700°C in a vacuum, the intensity of the 399.2 eV-peak is slightly decreased, and new peaks appear at 399.9, 400.7 and 402.4 eV. The 399.9, 400.7, and 402.4 eV-species are not formed when the nitrided oxide layers containing no 399.2 eV-species are heated at 700°C, showing that these species are produced from the 399.2 eV-species. Theoretical calculations using a density functional theory method show that O-N(-Si) 2 (nitrogen atom bound to two Si atoms and one oxygen atom) has an N 1s level shifted by þ1.3 eV from that of N(-Si) 3 , indicating that the 399.2 eV-peak is attributable to O-N(-Si) 2 . This species is likely to be easily formed by the insertion of N þ ions to the SiO 2 surface without an extensive atomic rearrangement. The calculations also show that O-N Å -Si (nitrogen radical bound to both one oxygen and Si atoms) and O@N-Si (nitrogen atom with an N@O double bond and an Si-N single bond) have þ1.8 and þ3.1 eV energy shifts, respectively, from the N 1s peak of the N(-Si) 3 species, leading to the attribution of the 399.9 eV-peak to O-N Å -Si and the 400.7 eV-peak to O@N-Si. The calculations also show that the 402.4 eV-peak is attributable to [N(-Si) 4 ] þ (a cation composed by a nitrogen atom bound to four Si atoms). The concentrations of the [N(-Si) 4 ] þ and O@N-Si species are almost constant throughout the nitrided oxide layers, showing that these species result from the reaction between O-N(-Si) 2 and bulk SiO 2 . The concentration of O-N Å -Si species, on the other hand, is low at the surface and high near the interface, showing that O-N Å -Si is formed by the reaction with Si.
Japanese Journal of Applied Physics, 2003
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Microstructural characterization of stoichiometric buried Si3N4 films
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
The properties of buried stoichiometric Si,N, 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 "N ions and a fluency of 1.4 X 10" at./cm* 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 a-SisN4 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.