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Unformatted text preview: The composition of ultrathin silicon oxynitrides thermally grown in nitric oxide E. P. Gusev, H. C. Lu, T. Gustafsson, and E. Garfunkel a) Departments of Physics and Chemistry, and Laboratory for Surface Modification, Rutgers University, Piscataway, New Jersey 08855 M. L. Green and D. Brasen Bell Laboratories Lucent Technologies, Murray Hill, New Jersey 07974 ~ Received 10 January 1997; accepted for publication 8 April 1997 ! The thermal oxynitridation of Si ~ 100 ! in nitric oxide ~ NO ! has been studied by high resolution medium energy ion scattering for ultrathin films. The nitrogen depth distribution and the composition of the films have been accurately determined. It is observed that for NO-grown films the nitrogen is distributed relatively evenly in the film, unlike the sharply peaked distribution observed in the case of SiO 2 films that were subsequently annealed in NO. The width of the nitrogen distribution, as well as the oxynitride thickness, increase with temperature. It is further found that the total amount of nitrogen in the film and the ratio of nitrogen to oxygen increases with increasing oxynitridation temperature. These results have significant impact on our understanding of how nitrogen can be positioned in next-generation gate dielectrics. © 1997 American Institute of Physics. @ S0021-8979 ~ 97 ! 01114-6 # Ultrathin ~ , 5 nm ! silicon oxynitrides (SiO x N y ) are the leading candidates to replace conventional oxides (SiO 2 ) as the gate dielectric in MOSFETs and as the tunnel dielectric in EEPROMs. Although it has been demonstrated that oxyni- tride gate dielectrics have a number of properties superior to conventional oxides ~ such as supressed boron penetration, improved hot electron immunity, and fewer interface de- fects ! , oxynitrides still have to be optimized in terms of both device performance and processing. 1–11 Furthermore despite some progress in a basic scientific understanding of ultrathin oxynitrides, 1–11 several fundamental questions, in particular the oxynitridation mechanism, and the reasons why the ni- trogen atoms in the film have a beneficial influence, are still not well understood. Also, the nitrogen depth distribution of these ultrathin films is not well known. Several recipes for nitrogen incorporation employing thermal oxidation/annealing 1,4,5,7,9–19 ~ in N 2 O, NO, NH 3 ! and deposition of oxynitrides 20–23 have been explored. Hydrogen-free oxynitridation in N 2 O is particularly attrac- tive because it allows one to incorporate what appears to be an appropriate amount of nitrogen near the SiO x N y /Si inter- face ~ typically ; 5 3 10 14 atoms/cm 2 ! , and due to its process- ing similarity to O 2 , N 2 O can replace oxygen in oxidation reactors/furnaces....
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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.
- Spring '09