New Photoresist Materials for 157-nm Lithography. Poly[Vinylsulfonyl Fluoride-<i>c</i><i>o</i>-4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropyl)-styrene] Partially Protected with <i>tert-</i>Butoxycarbonyl

Abstract

Our molecular orbital calculations predicted excellent transparencies of molecules having sulfonyl fluoride groups in the vacuum ultraviolet (VUV) region. An optical density (OD) measurement of poly(vinylsulfonyl fluoride) [poly(VSF)] prepared by free radical polymerization of VSF clearly supported this calculation (OD = 2.1 μm - 1 at 157 nm). A new copolymer, poly[(VSF) 40 - co -4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropyl)styrene (HFISt) 60 ] [poly(VSF 40 - co -HFISt 60 )] prepared by free radical copolymerization of VSF and HFIST showed good transparency (OD = 2.4 μm - 1 ) as well. Poly(VSF 40 - co -HFISt 22 - co - tert -butoxycarbonyl HFISt 38 ) (OD = 2.8 μm - 1 ) was prepared from poly(VSF 40 - co -HFISt 60 ) and di- tert- butyl dicarbonate in the presence of 4-(dimethylamino)pyridine (DMAP). A resist film consisting of poly(VSF 40 - co -HFISt 22 - co - tert- Boc HFISt 38 ) and 5 wt % triphenylsulfonium triflate showed a sensitivity of 7.2 mJ cm - 2 and a contrast of 3.1 when a 150-nm-thick film prebaked at 100 °C for 1 min was exposed to 157-nm laser, postbaked at 130 °C for 1 min, and developed with a 2.38 wt % tetramethylammonium hydroxide (TMAH) aqueous solution.