Hydrogenated Silicon-Oxynitride Film Antireflective Layer for Optical Lithography

Abstract

We present a theoretical method for antireflective layer (ARL) optimization in optical lithography and report the performance of hydrogenated silicon oxynitride ( SiOx Ny :H) film used as an ARL for krypton fluoride (KrF) excimer laser lithography. The optimum optical conditions of an ARL for tungsten silicide (W–Si) and aluminum silicon (Al–Si) substrates, which minimize the fluctuation of energy absorption in photoresists for photoresist thickness variations, are investigated. There are two types of optimum optical conditions, which give zero reflectance with the first and second cycle in thin film interference effects in an ARL, respectively. A type of SiOx Ny :H, which can satisfy the optimum optical conditions of an ARL for W–Si and Al–Si substrates, was found from the standpoints of its spectroscopic characteristics. Refractive indices of SiOx Ny :H film at the wavelength of 248 nm can be controlled by varying the deposition conditions in a plasma-enhanced chemical vapor deposition system. The variations in critical dimension caused by the thin-film interference effects in the photoresist for W–Si and Al–Si substrates are drastically reduced to within 0.02 µ m for 0.30 µ m patterns using this SiOx Ny :H film. Moreover, these SiOx Ny :H films can be left in the device structure without any influence on the electronic characteristics.