Incorporation of oxygen and nitrogen in ultrathin films of SiO/sub 2 annealed in NO

The areal densities of oxygen and nitrogen incorporated into ultrathin films of silicon dioxide during rapid thermal processing in nitric oxide, as well as the regions where these incorporations took place, were determined by combining nuclear reaction analysis and narrow nuclear resonance depth profiling with isotopic enrichment of the processing gas. Oxygen is seen to incorporate in the near-surface and near-interface regions of the oxynitride films, whereas nitrogen is incorporated only in the near-interface regions. The growth of the oxynitride film is very moderate as compared to that of a SiO2 film in dry O2 . The thermal oxynitridation of ultrathin SiO2 films takes place by two mechanisms in parallel: the major part of the NO molecules, which react with the silica, decompose in the near-surface region, the O atoms being exchanged for O atoms preexistent in this region of the SiO2 films; a minor portion of the NO molecules diffuse through the silica film in interstitial sites, without reacting with it, to react at the oxynitride/Si interface

The contribution of stable isotopic tracing, narrow nuclear resonance depth profiling, and a simple stochastic theory of charged particle energy loss to studies of the dry thermal oxidation of SiC

15th International Workshop on Inelastic Ion-Surface Collisions (IISC-15), Ise Shima, JAPAN, OCT 17-22, 2004International audienceWe present the stochastic approach to calculating fast charged particle energy distributions when penetrating matter, and nuclear reaction yield curves obtained when the energy of a beam incident on a target is scanned about the energy of narrow nuclear resonances, such as O-18(p,alpha)N-15 at 151 keV. In particular we present new calculations that show the insensitivity of the final calculations to the detailed form of the energy loss distribution assumed for independent single ion-atom collisions. We present application of narrow resonance profiling with O-18 stable isotopic tracing to the study of the dry thermal oxidation mechanisms of silicon carbide, yielding insights into the process that cannot be obtained by other means. (c) 2005 Elsevier B.V. All rights reserved

Growth of SiO2 on SiC by dry thermal oxidation: mechanisms

International audienceSiC is unique amongst the wide bandgap semiconductors in that the natural thermal oxide is stoichiometric SiO2, as is the case for silicon. The possibility of producing devices such as MOSFET in which thermal SiO2 is used as the gate insulator has motivated substantial work aimed at understanding the morphology and electrical properties of the SiO2/ SiC interface and the processes responsible for thermal oxide growth. The oxide growth kinetics are quite different, parallel and anti- parallel to the crystal polar direction. We review the experimental study of the nature of the thermal oxide grown in ultra- dry oxygen and of the extended interfacial region at the SiO2/ SiC interface on the nominally Si- terminated and C- terminated polar surfaces of hexagonal polytypes of SiC, highlighting how the use of stable isotopic tracing has helped to clarify processes for which kinetics measurements alone do not prove to be sufficiently incisive

Thermal ammonia nitridation on HfO2 and hafnium silicates thin films

17th International Conference on Ion Beam Analysis, Seville, SPAIN, JUN 26-JUL 01, 2005International audienceIn this paper we use isotopic tracing experiments with (NH3)-N-15 and (NH3)-N-14 to investigate the nitridation mechanisms on both hafnium silicates films (40-175 angstrom) and HfO2 (50 angstrom) films deposited by MOCVD on silicon substrate covered by a 10-15 angstrom interfacial SiO2 layer. Nitrogen profiles in the films were obtained through nuclear resonance profiling (NRP) with the N-15(p,alpha gamma)C-12 resonance at 429 keV and the total amounts of atomic species and the overall stoichiometry were obtained by RBS and NRA. In the silicate films, nitrogen is incorporated both into surface and bulk regions. For HfO2, lowering the ammonia pressure favors the fixation of nitrogen in the near surface region of film. This phenomenon is not observed in the case of silicate films. The pressure dependence of near surface nitrogen incorporation in HfO2 films could be related to the formation of oxygen vacancies and opens a way to control the diffusion barrier needed in the gate dielectric. (c) 2006 Elsevier B.V. All rights reserved

Defect and composition analysis of as-deposited and nitrided (100)Si/SiO2/Hf1-xSixO2 stacks by electron paramagnetic resonance and ion beam analysis

International audienceThe defects in the as-deposited and nitrided Si/SiO2/Hf1-xSiO(2) stacks have been analysed by EPR spectroscopy. The interface defects at the Si/SiO2 section are identical to those in the classical Si/SiO2 case and their concentration is not influenced by the hafnium silicate layer growth. As deposited hafnium silicate layers present in addition a defect located in the near surface region with a high concentration; it shows the characteristics of the EX center in SiO2 including low temperature hydrogen passivation. In the nitrided samples both the interface defects and the EX center are no longer observed. Additional annealing shows this to be related to a hydrogen passivation during the nitridation. The composition of the as deposited Hf1-xSixO2 layers have been analysed by ion beam analysis. Their thermal nitridation by NH3 has been investigated as a function of the annealing conditions. The hafnium silicate layers incoporate N up to some at% in the entire layer whereas hafnium oxide layers show no significant nitrogen incorporate into the bulk of the film

XPS and NRA investigations during the fabrication of gold nanostructured functionalized screen-printed sensors for the detection of metallic pollutants

International audienceAn all covalent nanostructured lead sensor was built by the successive grafting of gold nanoparticles and carboxylic ligands at the surface of self-adhesive carbon screen-printed electrodes (SPEs). Surface analysis techniques were used in each step in order to investigate the structuration of this sensor. The self-adhesive surfaces were made from the electrochemical grafting of p-phenylenediamine at the surface of the SPEs via diazonium salts chemistry. The quantity of grafted aniline functions, estimated by Nuclear Reaction Analysis (NRA) performed with p-phenylenediamine labelled with 15N isotope, is in agreement with an almost complete coverage of the electrode surface. The subsequent diazotization of the aniline functions at the surface of the SPEs was performed; X-ray Photoelectron Spectroscopy (XPS) allowed us to consider a quantitative conversion of the aniline functions into diazonium moieties. The spontaneous grafting of gold nanoparticles on the as-obtained reactive surfaces ensures the nanostructuration of the material, and XPS studies showed that the covalent bonding of the gold nanoparticles at the surface of the SPEs induces a change both in the Au-4f (gold nanoparticles) and Cl-2p (carbon ink) core level signals. These unusual observations are explained by an interaction between the carbon ink constituting the substrate and the gold nanoparticles. Heavy and toxic metals are considered of major environmental concern because of their non-biodegradability. In a final step, the grafting of the carboxylic ligands at the surface of the SPEs and an accumulation step in the presence of lead(II) cations allowed us to evidence the interest of nanostructured materials as metallic pollutants sensors

Merlú : revista de Radio Zamora: 1976

We investigated the mechanisms of thermal reoxidation in dry O2 of silicon oxynitride films prepared by processing Si~100! wafers in a rapid thermal furnace in a pure nitrous oxide ~N2O! ambient, using isotopic tracing of oxygen and nitrogen. Standard nuclear reaction analyses for the measurement of the total amounts of the different isotopes, and very narrow resonant nuclear reactions for high resolution ~1 nm! depth profiling of these elements were used. The silicon oxynitride films grown in pure 15N2 16O were 8-nm thick, with a small amount of nitrogen localized near the interfacial region. Under reoxidation in dry 18O2 , the thickness of the dielectric film increased while a pronounced isotopic exchange took place between the 18O from the gas and the 16O from the film, as well as a significant loss of 15N. This is in contrast with the reoxidation in dry O2 of pure SiO2 films, where the oxygen exchange is rather small as compared to that observed in the present case

The effects of ion implantation through very thin silicon oxide films

The ion implantation of heavy dopant species through very thin silicon oxide gate insulators degrades the insulating properties of the oxide inducing an enhanced leakage current in MOS siructures as well as a decrease of the dielectric breakdown voltage. In the present work we study quantitatively the possible physico-chemical causes of these degradation phenomena and of their recovery by thermal annealing using 18 O isotopic tracing techniques