High-rate (> 1 nm/s) plasma deposited a-SiNx:H films for mc-Si solar cell application

We present hydrogenated amorphous silicon nitride (a-SiN_x:H) films for multicrystalline silicon (mc-Si) solar cells that are deposited at high rate (> 1nm/s) using an expanding thermal plasma. This remote plasma technique permits one to deposit a-SiN_x:H with good antireflection coating properties and induces bulk passivation in mc-Si solar cells. The latter was observed by an enhanced red response of the cells´ internal quantum efficiency. Here, we focus on the complete characterization of a-SiN_x:H films deposited under various conditions from N₂/SiH₄ and NH₃/SiH₄ mixtures. The film properties of a-SiN_x:H are found to be determined mainly by the N/Si ratio ranging from Si-rich to near-stoichiometric N-rich films. A study of hydrogen evolution after a thermal anneal by a firing-through process shows two distinctive regimes in terms of the N/Si ratio and the mass density of the a-SiN_x:H films.