The diffusion of ion implanted hydrogen in amorphous Si3N4:H films

The tracer diffusion of hydrogen is studied in amorphous Si3N4:H films which were produced by rf magnetron reactive sputtering. The diffusion experiments were carried out in the temperature range between 700 and 1000 deg. C with ion implanted deuterium isotopes. Secondary ion mass spectrometry was used for depth profile analysis. While a considerable part of the tracer is immobilized due to the interaction with the implantation damage, the other part migrates freely into the film, wherefrom diffusivities are extracted. These diffusivities coincide with those obtained from a control experiment with a gas exchange technique, demonstrating that the implantation damage has no significant influence on the determination of the correct diffusivities themselves.2H transport can be described by the concept of trap limited diffusion, where the tracer atoms are temporarily trapped by intrinsic film defects, presumably nitrogen dangling bonds. For the present case of a considerably high dissociation rate of trapped hydrogen, effective diffusivities are derived which obey an Arrhenius behaviour with a large activation energy of ΔE = 3.4 eV and a pre-exponential factor of D0 5 x 10-4 m2 s-1. The effect on diffusion of pre-annealing the films prior to diffusion in nitrogen and possible structural rearrangements involved, as well as of charging the films with hydrogen up to 2.6 at.%, is analysed