Synthesis and application of polymers for 193-nm photoresists

Abstract

Norbornene-based copolymers containing 7,7-dimethyloxepan-2-one acid labile groups were synthesized and evaluated as potential nonshrinkable chemically amplified photoresists for ArF lithography. The 7,7-dimethyloxepan-2-one group of the matrix polymer was readily cleaved and the carboxylic acid functionality was formed by acid-catalyzed ring-opening reaction in the exposed region after post-exposure bake. Poly(3-(bicyclo[2.2.1]hept-5-en-2-ylhydroxymethyl)-7,7-dimethyl-oxepan-2-one-co-5-((2-decahydronaphthyl)oxycarbonyl)-norbornene-co-5-norbornene-2-carboxylic acid-co-maleic anhydride) was synthesized. 0.11 $\mu m$ line and space patterns were obtained at a dose of 10 mJ $cm^{-2}$ with a conventional developer, 2.38 wt% tetramethylammonium hydroxide aqueous solution, using an ArF excimer laser stepper. A norbornene-based monomer, methyl 4-(14-bicyclo[2.2.1]hept-5-en-2-ylcarbonyloxy-6,11-dimethyl-7-oxa-8-oxotetracyclo$[8.8.0.0^{2,6}.0^{11,16}]$ - octadec-5-yl)pentanoate (MBDMOP) having steroid derivative was synthesized and was copolymerized with maleic anhydride (MA) by free radical polymerization. The polymer, poly(MBDMOP-co-MA), exhibited relatively good transmittance at 193-nm and good thermal stability up to $260^\circ C$. With the conventional 2.38 wt% tetramethylammonium hydroxide (TMAH) developer, the resist formulated with poly(MBDMOP-co-MA) gaved $0.20-0.30 \mu m$ line and space patterns at a dose of 9 mJ $cm^{-2}$ using an an ArF excimer laser stepper. New silicon-containing polymers, poly(5-((2-trimethylsilyl-2-propyl)oxycarbonyl)-norbornene-co-maleic anhydride) (poly(TMSPN-co-MA)) and poly(5-((2-trimethylsilyl-2-propyl)oxycarbonyl)-norbornene -co-maleic anhydride-co-2-tri-methylsilyl-2-propyl methacrylate) (poly(TMSPN-co-MA-co-TMSPMA)), were synthesized and evaluated as dually developable chemically amplified photoresists. The polymers exhibited relatively good transmittances at 193-nm and have good thermal stability up to $195^\circ C$. The a...