Optimization of PECVD-Deposited SiOxNy Films: Investigating Compositional Dependency of Functional Properties

Abstract

Silicon oxynitride (SiON) thin films, fabricated via plasma enhanced chemical vapor deposition (PECVD), are highly promising for advanced microelectronics and lithography applications due to their tunable composition. This study investigates the precise modulation of refractive index and dielectric constant of PECVD SiON films, highlighting their potential as applications in photonic devices, dielectric insulation, and bottom anti-reflective coating (BARC) in electron beam lithography (EBL) processes. Accordingly, this research explores the effects of the Si:O:N stoichiometric ratio-a key determinant of SiON film properties-along with surface oxidation mechanism and density variations. It was observed that the refractive index can be tuned from 1.55 to 2.23 by varying the film composition between silicon oxide and silicon nitride thin films, thereby controlling their optical properties. Furthermore, post-annealing was found to modify the degree of oxidation, positively impacting the film’s stability against further oxidation. The optimized SiON films demonstrated considerable potential as BARC in the EBL process, effectively reducing the proximity effect and improving the lithographic resolution. For characterization, the refractive index and lithography patterns were evaluated using an ellipsometer and atomic force microscopy (AFM), respectively. Fourier transform infrared (FT-IR) spectroscopy and X-ray reflectivity (XRR) analyses were performed to investigate chemical bonding and density changes in sub-10 nm ultrathin films. X-ray photoelectron spectroscopy (XPS) depth profiling and peak deconvolution were utilized to quantitatively analyze the oxidation states on thin film surface. The results of this study provide valuable insights into the compositional engineering of SiON films, contributing significantly to the development of next-generation nanoscale device fabrication processes.