For integrated circuits, the integrity and film quality of the final passivation layer plays an important role in the device performance and reliability. Hydrogenated amorphous silicon oxynitride (α-SixNyOz:H) films deposited by plasma enhanced chemical vapor deposition (PECVD) have been extensively used for final device passivation applications. In this paper, a detailed characterization of PECVD oxynitride process for 200 mm Si wafer processing is presented. Silicon oxynitride of various compositions were deposited by changing the amounts of silane, ammonia, nitrogen and nitrous oxide in the reactant gas stream. Ultraviolet/Visible (UV/VIS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Rutherford backscattering spectrometry (RBS), and refractive index measurements were used to examine the variation in physical, optical and electrical properties. A correlation is observed between the oxynitride film composition, mainly N-H/Si-H ratio, and UV transmissivity (UV %T) which is of particular interest for memory applications. Effects of oxynitride film quality on e-test parameters and device performance are discussed.