Origins of silicon solar cell passivation by SiNx:H anneal

The origin of silicon solar cell passivation by the post-deposition anneal of hydrogenated silicon nitride (SiNx:H) anti-reflection (AR) coatings is investigated. The diffusion of hydrogen (H) in SiNx:H is dominated by fast diffusion of molecular hydrogen (H-2) and ammonia (NH3) and not by slow atomic diffusion through covalent bonding sites. An anneal of the SiNx:H layers leads therefore to a rapid H loss into the environment and not into the silicon bulk. Instead of bulk passivation by H atoms, the improvement of the electronic properties is due to art Si/SiNx:H-interface passivation caused by the formation of a few monolayers of silicon dioxide, which removes the bonding topology related stress at the interface. Secondary ion mass spectroscopy (SIMS) scans on various Si/SiNx:H stacks with mono- and polycrystalline substrates and remote and direct plasma enhanced chemical vapor deposited nitrides were carried out and showed strong interface accumulation of oxygen. (C) 2002 Elsevier Science B.V. All rights reserved.