Trinuclear Tin Complexes for Advanced Lithography: Sensitivity Enhancement via the Synergistic Effect in Dual Cross-Linking Systems

Balancing nanoscale pattern fidelity with high sensitivity remains a key challenge in extreme ultraviolet (EUV) lithography applications. Trinuclear tin complexes (organotin-based trinuclear macrocyclic complexes) have been shown to exhibit nanoscale pattern fidelity and demonstrate significant potential in enhancing sensitivity and reducing roughness caused by photon shot noise. This study investigates first how organic groups affect trinuclear tin complex photoresist sensitivity by investigating four trinuclear tin complexes with varying groups, and complex Vi-Sn-Oc {[{(nOc)₂Sn(5-Vi-1,3-bdc)}₃], (5-Vi-1,3-bdc = 5-vinyl-1,3-benzenedicarboxylate)} with CC bonds and long alkyl groups exhibits excellent sensitivity (D₀ = 23 μC/cm²) and high-resolution patterning performance in electron beam lithography (periodic lines of 16 nm and grid patterns of 13 nm) and EUV lithography (periodic lines of 20 nm). This confirms that trinuclear tin complexes can achieve nanoscale pattern fidelity at high sensitivity. Mechanistic studies on radiation exposure explain the solubility changes before and after exposure and the extremely high sensitivity of Vi-Sn-Oc. Specifically, the sensitivity enhancement of Vi-Sn-Oc arises from the synergistic effect in dual cross-linking systems, which includes Sn-X-Sn (X = O/alkylene) cross-linking at the Sn centers and CC cross-linking at the CC bonds. This novel synergistic mechanism may provide insights into the advancement of high-sensitivity, high-resolution tin-oxide EUV photoresists.