This invention relates to a method of fabrication used for semiconductor integrated circuit devices, and more specifically, to improve the photolithography processing window of a multi-layered dual damascene process by using a dielectric anti-reflective coating, DARC, comprised of multiple layers of silicon oxynitride, SiON, with varying k, dielectric constant values and thickness, to reduce reflectivity and improve light absorption. By varying both the thickness and the dielectric constant of the layers, the optical properties of light absorption, refractive indices, and light reflection are optimized.