Dissolution behavior of fluoroalcohol substituted polystyrenes

alpha-Fluoroalcohols have been proposed as transparent, base-soluble functional groups for use in the design of new 157 nm photoresist polymers. The two most common and easily prepared fluoroisopropanol groups are bis-trifluoromethyl carbinols (hexafluoroalcohol) and methyl-trifluoromethyl carbinols (trifluoroalcohol). This paper describes studies designed to assess the suitability of both of these functionalities as acidic groups. Dissolution rate studies were carried out on polystyrene films that incorporate these groups. The dissolution rates of the sample polymers were compared to that of poly(hydroxystyrene) (PHOST) to provide a reference for the measurements. It was found that the trifluoroalcohol polymers do not exhibit any solubility in basic media, while the hexafluoroalcohol polymers dissolve rapidly relative to PHOST in 0.13N TMAH. Further, it was found that the two fluoroalcohol polymers can be blended to adjust the inherent dissolution rate of the resin and that the hexafluoroalcohol polymer is sensitive to incorporation of classical dissolution inhibitors. The study concludes that hexafluoroalcohol is a promising candidate for incorporation into the design of 157 nm photoresists.