The structure of defects of SiNx:H films is investigated by electron-spin r
esonance. It is found that a relaxation process takes place at annealing te
mperatures below 600 degrees C for those compositions in which the nitrogen
-to-silicon ratio is above the percolation threshold of the Si-Si bonds in
the nitride lattice. The nature of this process is discussed and attributed
to a thermally activated charge transfer between metastable defects. No su
ch relaxation occurs in the films with a composition below the percolation
threshold, possibly due to a positive correlation energy and a structural l
ack of flexibility. For higher annealing temperatures, an increase of the d
efect density is observed and associated with the thermal release of hydrog
en. (C) 2000 American Institute of Physics. [S0021-8979(00)00516-8].