Evaluation and Characterization of High-Uniformity SiN_x Thin Film with Controllable Refractive Index by Home-Made...

Silicon nitride (SiN_x) thin film is a promising coating with great physiochemical and optical properties. However, the preparation of films with good comprehensive properties still faces challenges. This study focused on developing a method for the preparation of uniform SiN_x thin film with a controllable refractive index using home-made catalytic chemical vapor deposition (Cat-CVD) equipment. Orthogonal experimental design was employed to investigate the effects of four key influence factors, including reaction pressure, the ratio of SiH₄ to NH₃, the ratio of SiH₄ to H₂, and substrate temperature. The response parameters evaluated were the refractive index, extinction coefficient, uniformity, and deposition rate of SiN_x thin film. Compared with the single-factor variable tests, an orthogonal experiment could obtain the optimal preparation process of the SiN_x thin film with the best comprehensive quality through the least number of experiments. At the same time, the microstructures of SiN_x thin film were analyzed by various characterization methods, including Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), to research the relationship between preparation factors and the properties of SiN_x thin film. This paper provides the theoretical guidance for fine-regulating the properties of SiNx thin film in practical applications.