The release of H and N from amorphous dielectrics was studied by means of MeV ion-scattering spectrometry and infra-red spectroscopy. The out-diffusion of these constituents was activated by rapid thermal annealing. Molecular models for the process were proposed on the basis of information obtained from infra-red spectra, and the validity of the models was tested by analyzing the activation energy of the desorption process. The evolution of the H concentration, as a function of annealing temperature, was fitted to an Arrhenius-type law which was derived from a second-order kinetic formulation of the reactions which were described by the present structural model. It was found that low values of the activation energy could be explained by the formation of H-bonding interactions between Si-H or N-H groups, and nearby doubly-occupied N orbitals. This electrostatic interaction weakened the Si-H or N-H bond and favored the release of H. The detailed mechanism of this process, and the temperature range within which it operated, depended upon the amount and proportion of H in the Si-H and N-H bonds. Samples with a higher N content, in which all of the bonded H was in the form of N-H bonds, were more stable to annealing than were samples in which both Si-H and N-H bonds were detected. In the latter N-rich films, only a loss of H was detected at the highest annealing temperatures.

Molecular Models and Activation Energies for Bonding Rearrangement in Plasma-Deposited a-SiNx:H Dielectric Thin Films Treated by Rapid Thermal Annealing. F.L.Martínez, A.Del Prado, I.Mártil, G.González-Diaz, W.Bohne, W.Fuhs, J.Röhrich, B.Selle, I.Sieber: Physical Review B, 2001, 63[24], 245320 (11pp)