Microstructure Characterization of Amorphous Silicon-Nitride Films by Effusion Measurements

The microstructure of a-Si:N:H films, which are applied as antireflection coating and for defect passivation in multicrystalline silicon (mc-Si) solar cells, was studied by gas effusion experiments. The results show for as-deposited material of low substrate temperatures (TS = 200 – 300°C) a predominant diffusion of molecular hydrogen for temperatures up to 800°C in agreement with the presence of interconnected openings (voids). At higher substrate temperatures, the material has a more compact structure and atomic hydrogen is the dominant diffusing species in the accessible temperature range. Annealing effects were also studied. The results are consistent with the concept that atomic hydrogen released from the a-Si:N:H coating serves for defect passivation in μc-Si solar cells.