An antireflection coating structure comprised of metal (copper) nanoparticles over silicon nitride has been numerically investigated. The structure is embedded between semi-infinite vacuum and silicon substrate and a TE plane polarized wave is incident on the proposed structure. The permittivity of all the involved materials in the proposed structure is wavelength dependent. Numerical results are presented to show the effects of the incidence angle, the wavelength, and the structure parameters on the reflection coefficient. The antireflection coating structure and the obtained results could be useful for design of future solar cells and optical sensors.