Diffusion studies in magnetron sputter deposited silicon nitride films

In this work, silicon nitride coatings were deposited by magnetron sputtering onto float glass substrates and post-deposition annealed at 650 °C for 5 min. The structures and compositions of the coatings were investigated by X-ray diffraction, X-ray reflectometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Samples were then over-coated with silver and subjected to a second annealing process to initiate the diffusion of silver through the adjacent coating layers. Additional silicon nitride coatings were then deposited on selected samples to produce Si3N4/Ag/Si3N4/glass stacks, which were annealed at temperatures in the range 100-600 °C. Ag and Na diffusion coefficients were then calculated from compositional profiles obtained from time of flight secondary ion mass spectrometry analysis. The coatings deposited in this study were found to have stoichiometric Si3N4 compositions and were amorphous after annealing. The diffusion rate of silver through these coatings was found to depend on annealing temperature and coating density and roughness, which in turn can be related to the deposition conditions.