Silicon carbon nitride (SiCN) thin films are promising materials for copper diffusion barriers and hybrid bonding in semiconductor processes. Oxidation-resistant films are increasingly critical for realizing high-reliability devices, highlighting the need for process control and property evaluation. In this study, we analyzed the thin film properties as a function of tetramethylsilane (4MS) gas partial pressure ratio (PPR), deposition temperature, and dual-power plasma conditions in a PECVD-based SiCN deposition process. Based on the results, we experimentally demonstrated that the refractive index can be a valid indicator for oxidation resistance evaluation. The application of dual-power plasma conditions was instrumental in enhancing oxidation resistance. Under these conditions, the refractive index reached approximately 1.90 even at 200℃, comparable to values observed in films deposited at 350℃. These findings provide a basis for predicting oxidation resistance and optimizing low-temperature conditions, with applications in next-generation semiconductor and packaging technologies requiring high reliability.