Defect structure of SiNx:H films and its evolution with annealing temperature

The structure of defects of SiNx:H films is investigated by electron-spin resonance. It is found that a relaxation process takes place at annealing temperatures below 600 °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 such relaxation occurs in the films with a composition below the percolation threshold, possibly due to a positive correlation energy and a structural lack of flexibility. For higher annealing temperatures, an increase of the defect density is observed and associated with the thermal release of hydrogen.