Dendrimer-based chemically amplified resists for sub-100-nm lithography

Abstract

Several new poly(benzyl ether) and poly(benzyl ester) dendrimers that incorporate acid- and thermally- labile peripheral groups have been synthesized. Tertiary butyl ester terminated poly(benzyl ether) dendrimers were synthesized using (alpha) -bromo-t-butyl acetate in the preliminary protection step to afford the first generation alcohol. A standard bromination of the focal point benzylic alcohol was used for the activation step, while standard Williamson ether conditions were used for the coupling steps to afford higher generation poly(benzyl ether) dendrons. Tertiary butyl ester terminated dendrons were then coupled to a difunctional core to produce the [G-3] dendrimer. Tertiary butyl carbonate (t-Boc) terminated poly(benzyl ester) dendrimers were also synthesized. This class of dendrimers was synthesized by first protecting monomeric building block 3,5-dihydroxybenzaldehyde with di-t-butyl dicarbonate. A reductive activation step afforded the [G-1] alcohol. The growth steps were accomplished by either Mitsunobu etherification with 3,5- dihydroxybenzaldehyde or by esterification with 5- hydroxymethylisophthalic acid. Finally, coupling of the benzyl alcohol dendrons to a polyfunctional core afforded second and third generation dendrimers. Chemically amplified resists formulated from both t-butyl ester and t-Boc terminated dendrimers show high sensitivity to DUV and e-beam irradiation. Feature sizes well below 100 nm have been routinely patterned using e-beam lithography.