193-nm chemically amplified positive resists based on poly(norbornene-alt-maleic anhydride) with plasticizing additives

Abstract

The lithographic performance and environmental stability of 193 nm chemically amplified resists based on norbornene t- butyl ester/maleic anhydride copolymer were investigated. Tert-butyl (t-Bu) cholate was used as a plasticizing additive to control the glass transition temperatures (Tg) of the resists. The resist softening temperature was decreased from > 180 degrees Celsius to 150 degrees Celsius by the addition of t-Bu cholate. The resist sensitivity and resolution were almost unchanged, when post-exposure bake (PEB) temperatures were below the resist softening temperature. High environmental stability of 1 hour was achieved by optimizing the resist softening temperature, because high temperature baking at around the resist softening temperature reduced the amount of residual solvent, and thus made the resist absorb basic airborne contaminants less readily. The environmental stability of the optimized resist was almost the same as that of 248 nm acetal type resist, and it was sufficient for practical use.