Effects of fluorine for photoresist properties

Abstract

With new era of semiconductor industry, fluorine in photoresist is now becoming an interest of related researchers. In this study, effects of fluorine for photoresist properties ?lithographic evaluation, adhesion, UV absorbances and thermal property and so on - were investigated. Two monomers (1,1,1-Trifluoro-2-methyl-3-trimethylsilanyl-2-propyl methacrylate, 2-Methyl-1-trimethylsilanyl-2-propyl methacrylate) with same structure were synthesized. One monomer is different from the other one only that it has a trifluoro-substituted methyl group instead of methyl group. These monomers were co- or ter-polymerized with 2-methoxyethyl methacrylate. Poly(TFMTMSPMA-co-MEMA) is thermally more stable than poly(MTMSPMA-co-MEMA) and their glass transition temperature (Tg) were not detected. There wasn?t any significant differences in plasma etch rate between these polymers and their adhesion properties decreased according to the content of fluorine atoms. Poly(MTMSPMA-co-MEMA) with 3 mJ/㎠ exposure dose, no PEB and short development process shows fine patterns up to 0.8㎛. Additional PEB process or more development time for poly(MTMSPMA-co-MEMA) blur the L/S patterns because of fast dissolution of unexposed region. In the case of terpoly(TFMTMSPMA-MTMSPMA-MEMA), L/S patterns were obtained but dissolution of unexposed area was not completed. Poly(TFMTMSPMA-co-MEMA) shows no L/S pattern because there was no deprotection reaction in polymer because of strong electron-withdrawing effect of trifluoromethyl group.