抄録
Several strategies were employed to improve the transparency and etch resistance of the acrylate-based 157 nm photoresists. (1) α-Fluorinated acrylates were synthesized and polymerized using radical initiation. The homopolymer of 2-[4-(2-hydroxy-hexafluoroisopropyl)cyclohexane]hexafluoro isopropyl-α-monofluoroacrylate (FA) showed high transparency at 157 nm (A = 1.7 μm-1), and its copolymer with norbornene hexafluoroalcohol and α-fluoro-tert-butylacrylate shows good 248 nm lithographic performance. (2) Selected acrylates containing hexafluoroisopropyl groups and hydrogenated single ring and multi-ring systems were prepared to address etch resistance. Homopolymers of acrylic versions of FA with different alicyclic moieties such as 1,3-cyclohexane, hydrogenated diphenyl ether and decaline showed very good transparency at 157 nm (A = 1.8 μm-1, 2.4 μm-1, 2.6 μm-1, respectively). Tg values for these homopolymers were determined to be in the range of 91-95°C. (3) The POSS group was also used to improve etch resistance. POSS-containing non-fluorinated acrylate copolymers showed absorbances of 3.0-3.3 μm-1 at 157 nm. POSS containing α-trifluoromethylacrylate polymers are expected to have lower absorbance. (4) To utilize an alternating copolymerization scheme, new fluorinated monomers containing both electron-rich and electron-deficient double bonds in one molecule were synthesized. The monomers were designed to undergo cyclopolymerization to generate polymers for improved transparency, etch resistance and outgassing properties.
