Synthesis of fluorinated materials for 193-nm lithography

Various fluorinated polymers were synthesized for in 193-nm dry and immersion lithography with the goal of improving 157-nm photoresist performance. Their fundamental properties were characterized, such as transparency at 193-nm and 157-nm (wavelength) and solubility in water and a standard alkaline developer. High transparency, i.e., absorbance better than 0.2 μm^-1 at 193-nm wavelength, was achieved. The dissolution behaviors of them were studied by using the quartz crystal (QCM) method. We find that the dissolution rate of poly(norbornene-2-fluoro-2-hexafluoroalcohol) (PNB1FVIP) in 0.065N tetramethylammonium hydroxide (TMAH) was > 100 times (nm/s) faster than that of the copolymer of tetrafluoroethylene (TFE) and norbornene-2-fluoro-2-hexafluoroalcohol (TFE/NB1FVIP). A resist based on TFE/NB1FVIP was able to delineate 75 nm dense lines by exposure at 193-nm (wavelength) with an alternating phase shift mask using a 0.75 NA ArF scanner. The dissolution rates of the fluoropolymers in water and a 0.262N and 0.065 TMAH can be controlled by optimizing counter monomers containing hexafluoroisopropanol (HFA) unit, carboxylic acid unit and so on. In addition, we have collect water contact angle data. This data shows that fluoropolymers can be used as TARC for 248-nm and 193-nm lithography and top-coat for 193-nm immersion lithography resists.