469-baumvol-jap-1998-5579 - Effects of the surface...

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Unformatted text preview: Effects of the surface deposition of nitrogen on the thermal oxidation of silicon in O 2 I. J. R. Baumvol a) Instituto de Fı´sica, Universidade Federal do Rio Grande do Sul, 9500 Bento Gonc ¸alves, Avenue 91509-900 Porto Alegre RS, Brazil T. D. M. Salgado, F. C. Stedile, C. Radtke, and C. Krug Instituto de Quı´mica, Universidade Federal do Rio Grande do Sul, 9500 Bento Gonc ¸alves, Avenue 91509-900 Porto Alegre RS, Brazil ~ Received 27 October 1997; accepted for publication 14 February 1998 ! Nitrogen was deposited on the surface layers of Si ~ 100 ! by ion implantation at a very low energy ~ approximately 20 eV ! , at fluences between 1 and 10 3 10 14 cm 2 2 . The samples were thermally oxidized in dry O 2 at 1050 °C, and the areal densities and profiles of N and O were determined by nuclear reaction analysis and narrow nuclear resonance profiling, evidencing that: ~ i ! the retained amounts of N just after ion beam deposition stayed in the range between 0.3 and 7 3 10 14 cm 2 2 ; ~ ii ! the oxide growth is influenced strongly by the presence of nitrogen, the thickness of the oxide films ~ which remained between 4 and 30 nm ! decreased with the increase of the areal density of nitrogen; ~ iii ! N is partially removed from the system as oxidation proceeds. These observations are discussed in terms of current models for the thermal growth of silicon oxide in the presence of N. © 1998 American Institute of Physics. @ S0021-8979 ~ 98 ! 06310-5 # Silicon oxynitride presents several advantages over the oxide when used in sub-10 nm films for gate and tunnel dielectrics. It provides improved resistance to dopant diffu- sion, increased reliability, and enhanced resistance to hot car- rier degradation. 1–3 In particular, the thermal oxidation in O 2 of Si wafers previously implanted with N ions has been con- sidered recently as a route to prepare silicon oxynitride films for gate dielectrics in ultralarge scale integrated ~ ULSI ! metal-oxide semiconductor field effect transistor ~ MOSFET ! devices. 4–7 It has been known for a long time that the pres- ence of rather small concentrations of N ~ 1 at % and less ! slows down the thermal oxide ~ oxynitride ! growth in O 2 . 8 The effect of N implantation doses below and around the equivalent to 1 monolayer in reducing the rate of thermal growth of SiO 2 in dry O 2 has been reported previously. 4,9 Trimaille et al. 9 implanted 1 3 10 15 N cm 2 2 into Si through SiO 2 films, and continued the thermal growth of the im- planted film in O 2 , concluding that N inhibits only the near oxide/silicon interface region where growth takes place. This effect was corroborated by several authors 10,11 in the case of ultrathin ~ 5 nm ! oxynitride films thermally grown in N 2 O, whereas the thermal reoxidation in O 2 of thicker oxynitride films ( ; 10 nm), showed modifications on the near interface and near surface oxygen incorporations....
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This note was uploaded on 12/10/2009 for the course IF PFIS1200 taught by Professor Antonio during the Spring '09 term at Universidade Federal do Rio de Janeiro.

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469-baumvol-jap-1998-5579 - Effects of the surface...

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