Exposure dose-dependent multi-tone photolithography via photoacid-induced crosslinking and degradation of poly(2,3-dihydrofuran)

We propose an exposure dose-dependent multi-tone photolithographic strategy based on competing photoacid-induced crosslinking and degradation within a single homopolymer system. Poly(2,3-dihydrofuran) (PDHF), synthesized via ring-opening metathesis polymerization, integrates acid-triggered inter-chain cationic crosslinking and main-chain acid-catalyzed scission through enol ether moieties, enabling negative-tone, positive-tone, and edge-retained patterning without post-exposure baking. At low exposure doses, crosslinking dominates to generate negative-tone features, whereas high doses induce degradation to produce positive-tone patterns. Unlike conventional chemically amplified resists, the developed patterns consist of crosslinked networks, suppressing photoacid migration and reducing pattern blurring. This work demonstrates a dose-dependent multi-tone lithographic strategy based on photoacid-induced crosslinking and degradation within a single polymer system, offering insights into exposure-controlled pattern formation.