HYDROGENATED SILICON-OXYNITRIDE FILM ANTIREFLECTIVE LAYER FOR OPTICALLITHOGRAPHY

We present a theoretical method for antireflective layer (ARL) optimiz ation in optical lithography and report the performance of hydrogenate d silicon oxynitride (SiOxNy:H) film used as an ARL for krypton fluori de (KrF) excimer laser lithography. The optimum optical conditions of an ARL for tungsten silicide (W-Si) and aluminum silicon (Al-Si) subst rates, which minimize the fluctuation of energy absorption in photores ists for photoresist thickness variations, are investigated. There are two types of optimum optical conditions, which give zero reflectance with the first and second cycle ill thin Blm interference effects in a n ARL, respectively. A type of SiOxNy: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 SiOxNy:H him at the wavelength of 248 nm can be controlled by varying the deposition conditions in a plasma-enhanced chemical va por 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 mu m for 0.30 mu m patterns using this SiOxNy:H film. Moreover, these SiO2Ny:H films ca n be lek in the device structure without any influence on the electron ic characteristics.