Characterization and comparison of silicon nitride films deposited using two novel processes

Hydrogenated silicon nitride films (SiN_x:H) deposited using a PECVD process enhance the performance of crystalline silicon solar cells by functioning as an efficient anti-reflection coating and passivating layer. In this paper, we compared two novel SiN_x:H deposition processes using two different PECVD tools - one non-traditional in process regime, and the other non-traditional in type, to determine their suitability to solar cell fabrication. The parameter space was explored by employing a design of experiment methodology followed by material characterization using VASE, reflectance, FTIR and RBS/ERD. The thickness and reflectance of Si-rich films changed dramatically after annealing. Further, FTIR results showed that the Si-H bond peak present at 2160 cm^-1 in such films disappeared after a typical Al firing step. Therefore, the optimized films were deposited with a lower SiH₄/NH₃ ratio to minimize the changes in the film properties after annealing.