Properties and characterization of low-temperature amorphous PECVD silicon nitride films for solar cell passivation

Deposition conditions and some structural and electrical properties of amorphous silicon nitride (SixNy:H) films deposited on Si substrates have been studied for photovoltaic applications. A plasma enhanced chemical vapor deposition (PECVD) system has been used for the study. Experiments have been performed varying the flow ratios and dilution of the reactant gases. Increased hydrogen (H-2) dilution leads to reduced deposition rate and a better controllability in the growth process. The hydrogen content in the film also decreases with increasing H-2 dilution of the reactant gases. Flow ratio of the reactant gases (SiH4/NH3) also influences the growth rate. There is an optimal reactant gas mix to maximize the film growth rate. However, the film stoichiometry is also modified by changing the gas mix, with higher flow ratios resulting in Si-rich films. The level of interfacial recombination of minority carriers has been studied by capacitance-voltage and effective lifetime measurements. Bombardment by the energetic species in the plasma leads to plasma damage at the interface. These interfacial defects can be annealed by a post-deposition, low temperature treatment. (C) 2005 Springer Science + Business Media, Inc.