Synthesis, Radiation Degradation, and Electron Beam Resist Behavior of Fluorine‐Containing Vinyl Polymers

Abstract

Abstract : Novel vinyl monomers containing the a-CF3 group are shown to increase the propensity toward chain scission during radiation degradation and increase the electron beam sensitivity in copolymers with methyl methacrylate and methacrylonitrile. The incorporation of 32 m/o of a-trifluoro-methacrylonitrile (TFMAN) into poly(methyl methacrylate) increases sensitivity from 30 x 10 (expn -5) to 3 x 10 (expn 5 C/cm (expn 2) (at 2 keV), increases G sub 8 from 1.3 to 3.1, and decreases the etch rate from 100 to 79 Angstrom/min. Similar beneficial results come from incorporating TFMAN into methacrylonitrile (MCN) copolymers. Poly(trifluoroethyl methacrylate) is a highly sensitive resist (Q = 2 to 3 x 10 (expn -5) C/cm (expn 2)) but it exhibits a high etch rate (230 Angstrom/min). Incorporation of 31 m/o MCN into this polymer decreases the etch rate to 93 Angstrom/min while preserving a high sensitivity (3-4 x 10 (expn -5) C/cm (expn2)). The G sub 8 and G sub x values of these homo- and copolymer systems as well as the copolymer of methacrylonitrile with methyl a-fluoroacrylate (MFA) were obtained. The homopolymer of MFA cross-links on irradiation but its MCN copolymers tend to be positive resists with G sub x values lower than that expected if G sub x were a linear function of the MFA mole fraction.