Journal of Micro/Nanolithography, MEMS, and MOEMSApplication of polysilazane to etch mask in pattern transfer processes for deep and vacuum ultraviolet lithography
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A polysilazane is investigated for a spin-on glass (SOG) used for a middle layer in a trilevel resist system. Higher film density is required for the middle layer to obtain higher etch resistance during the underlayer etching. The compositions of the polysilazane baked at 200°C and 300°C are Si0.42O0.34C0.40N0.20 and Si0.29O0.65C0.10N0.05, respectively, which are determined by x-ray photoelectron spectroscopy. The polysilazane is converted to silicon-oxide-like compositions by baking at 300°C. The film density and etch rate of SOG made from polysilazane are compared with that of polysiloxsane on condition that both films are baked at 300°C. The film density of the SOG made from the polysilazane is 2.07 g/cm3, which is higher than 1.87 g/cm3 of the conventional SOG made from a polysiloxsan. The etch resistance of the SOG made from the polysilazane is improved by 90% compared with that of the SOG made from the polysiloxsane due to the increased film density.