Double-layer inorganic antireflective system for KrF lithography

A novel bottom antireflective method is described to resolve the problems i n conventional antireflective methods such as insufficient antireflection a nd dependence on substrate materials and structures. The proposed antirefle ctive method is composed of two layers. A high photoabsorption layer at the bottom absorbs most of the light reflected from the substrate and an inter ference layer at the top suppresses the surface reflection from the bottom layer. This new method can achieve extremely low substrate reflectivity (<0 .5%) for all substrates, and it provides a larger process window on film th ickness than conventional methods. Silicon oxynitride (SiOxNy:H-z) film was chosen as the bottom antireflective coating material. A new plasma-enhance d chemical-vapor deposition scheme with SiH4, N-2, N2O, and He as reactant gases was used to fabricate the SiOxNy:H-z films in order to obtain a wide variation of film optical properties. The compositional characteristics of the films were investigated by x-ray photoelectron spectroscopy. The comple x indices of refraction (n-ik) and thicknesses of the films were measured b y variable-angle spectroscopic ellipsometry. The film structure was analyze d by Fourier transform infrared spectroscopy. Comparing this method with th e conventional one using SiH4 and N2O as reactant gases, it provided a much wider range of film compositions that could easily meet the different requ irements in many different process applications. In order to produce high-q uality silicon oxynitride films and to enhance the extent of reaction betwe en SiH4 and N-2, the effects of substrate temperature, plasma power, and re actor chamber pressure were studied to find the optimum deposition conditio ns. Moreover, correlations of the n and k values with the SiOxNy:H-z stoich iometry were obtained. While the n values could be correlated with a linear relation to the atomic concentration ratio of [O]/([O]+[N]), the k values were determined exclusively by the silicon contents in the films. (C) 2000 American Vacuum Society.