In this study, a silicon oxy-nitride (SiOxNy) film deposited using the plasma enhanced chemical vapor deposition method has been developed and applied to improve poly-gate level resist line CD control. The desired optical properties of a SiOxNy anti-reflective coating (ARC) film and its optimum thickness were targeted by using a photolithography simulator. A process matrix study has led to the identification of an optimized SiOxNy film Dielectric ARC deposition process for i-line photolithography applications. Using the optimized SiOxNy film as the ARC, significant improvements, compared to the standard and top ARC techniques, have been achieved, including 5 times reduction in does to clear swing ratio and complete elimination of reflection induced photoresist notching and necking effects. Moreover, a 2500 wafer marathon run demonstrated that the refractive index, extinction coefficient and thickness of this film can be controlled to +/- 0.04, +/- 0.03 and +/- 12A, respectively and that the particle performance is excellent.