Thermally induced changes in the optical properties of SiN<inf>x</inf>:H films deposited by the electron cyclotron resonance plasma method

  • F. L. Martínez /
  • A. Del Prado /
  • I. Mártil /
  • G. González-Díaz /
  • B. Selle /
  • I. Sieber
Journal ar
Journal of Applied Physics
  • Volumen: 86
  • Número: 4
  • Fecha: 15 August 1999
  • Páginas: 2055-2061
  • ISSN: 00218979
  • Source Type: Journal
  • Document Type: Article
  • Publisher: American Institute of Physics Inc.
We analyze the effect of thermal processes on the optical properties (refractive index, optical gap, Taue coefficient, and Urbach energy) of SiNx:H films. Films with three different nitrogen to silicon ratios (x = 0.97, x = 1.43, and x = 1.55, respectively) were deposited by a chemical vapor deposition technique assisted by an electron cyclotron resonance generated plasma. After deposition they were subjected to rapid thermal annealing at temperatures ranging from 300 °C to 1050 °C. We found that the percolation threshold for Si-Si bonds (at x = 1.1) separates films with different response to thermal treatments. The changes of the Taue coefficient and the Urbach energy at moderate annealing temperatures indicate a structural relaxation of the network for the films with x above the percolation threshold, while at higher temperatures the trends are inverted. In the case of x below the percolation limit the inversion point is not observed. These trends are well correlated with the width of the Si-N infrared stretching absorption band. Additionally the samples with as-grown x = 1.43 show a good correlation between the Urbach energy and the density of unpaired spins in silicon dangling bonds. © 1999 American Institute of Physics.

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