Patterning of hyperbranched resist materials by e-beam

The application of a hyperbranched polymer with its globular architecture as a chemically amplified resist system is demonstrated. These hyperbranched poly(esters) based on 3,5-dihydroxybenzoic acid and 4,4-bis(4-hydroxyphenyl)valeric acid and obtained by a polycondensation process at high temperatures. Once obtained, the hyperbranched polymers are functionalized with acid and thermally labile t-BOC groups by reaction of their phenolic groups with di-t-butyl dicarbonate in the presence of a catalytic amount of potassium t-butoxide. These globular materials have number average molecular weights (M_n) in the range of 5,000-20,000 with polydispersities of 1.5-2. Exposure of the hyperbranched resist material formulated with a photoacid generator was carried out using a direct-write electron-beam (e-beam) tool operating at 50 keV with doses of 15-40 μC/cm². Development of these resist materials can be accomplished in either aqueous base developer or organic solvent, thereby allowing access to both the positive and negative tone images. Feature sizes of 100 nm are readily obtained from these unoptimized materials.