Organosilicate polymer e-beam resists with high resolution, sensitivity and stability



Hydrogen silsesquioxane (HSQ) is an attractive electron-beam (e-beam) resist for sub-20 nm lithography owing to its high resolution, excellent line-edge roughness (LER) and good plasma etch resistance. However, the sensitivity and long-term stability of HSQ need to be significantly improved to have HSQ resists adopted for volume manufacturing. Here we develop novel organosilicate e-beam resists with improved e-beam sensitivity and stability as an alternative to HSQ resists. Copolymers of norbornene ethyltrimethoxysilane (NETMS) with 1,2-bis(triethoxysilyl)ethane, synthesized via acid-catalyzed sol–gel reactions, show excellent e-beam sensitivity with around a sixfold reduction in the critical dose as compared with HSQ but poor LER characteristics. Terpolymers were then synthesized using p-chloromethylphenyl trimethoxysilane (p-CMPTMS), NETMS and tetraethoxysilane, which exhibit significant improvement in sensitivity as compared with previously reported materials, together with high-resolution patterns and long-term stability. High-resolution patterns of features as small as 20 nm with excellent LER were successfully fabricated employing organosilicate terpolymers using a 100 keV e-beam. The dose for patterning 20 nm lines was reduced from 4000 μC cm−2 for HSQ to 900 μC cm−2 for an optimized terpolymer resist. FT-IR measurements suggest that the main reason for the increased e-beam sensitivity is chain transfer reaction between the norbornene moieties, which provide an efficient cross-linking mechanism by the e-beam generated radicals. Copyright © 2013 John Wiley & Sons, Ltd.