The optical properties of silicon-rich silicon nitride prepared by plasma-enhanced chemical vapor deposition

This research investigated the optical properties of silicon-rich silicon nitride (Si-rich SiN) and conventional silicon nitride (SiNx) layers, which are commonly used in anti-reflective coating (ARC) to improve the light absorption in solar cells. We found that the change in the refractive index of Si-rich SiN was due to the annealing temperature that was considerably higher than that of conventional SiNx. In addition to the mass density variation in the SiNx layer that generally governed the change of refractive index in previous studies, this study found another important factor influencing the change of the refractive index. The Si-N bond, which was the main component in SiNx controlled the refractive index, while the amount of Si-Si bond in Si-rich SiN after annealing governed the change of the refractive index. The structural analysis presented for the Si-rich SiN and the SiNx explained the effect of the annealing process on tuning the refractive index of the Si-rich SiN.