Norbornene and Epoxide-Substituted Silsesquioxane Photoresists with High-Sensitivity and Stability

The evolution of photoresists has been accelerated by escalating demands for pattern fidelity, particularly with the breakthrough of extreme ultraviolet (EUV) lithography in achieving sub-20 nm resolution. Herein, we report two kinds of partially alkyl-substituted silsesquioxane (PASS) resists to overcome the dual challenges of hydrogen silsesquioxane (HSQ) in EUV applications: inherent instability and unsatisfactory sensitivity. Through strategic integration with a photoacid generator (PAG), the optimized formulation demonstrates exceptional lithographic performance, achieving 14 nm resolution (line edge roughness of 1.3 nm) with a sensitivity of 4.3 μC/cm² and a contrast of 5.1 under electron beam lithography. Besides, the PASS resist exhibits a 360-day gelation period and a 160-fold improvement over conventional HSQ. Systematic investigations combining micro-Raman spectroscopy and model compound studies reveal that PAG enhances both sensitivity and shelf stability through dual mechanisms: (1) a photoacid-catalyzed cross-linking reaction between siloxanes and (2) nucleophilic attack inhibition at silicon centers. These advances, coupled with successful electron-beam and ultraviolet patterning demonstrations and structural tunability, establish PASS resists as viable candidates for EUV lithography in semiconductor nanofabrication.