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 SiH ₄/NH ₃ ratio to minimize the changes in the film properties after annealing.