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 antireflection coating and passivating layer. In this paper, we compared two SiN_x:H novel deposition processes using two different PECVD tools—one nontraditional in process regime and the other nontraditional 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 variable angle spectroscopic ellipsometry, reflectance, FTIR, RBS and elastic recoil detection. 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.