Novel Sn-based photoresist for high aspect ratio patterning

Abstract

Extreme ultraviolet (EUV) lithography is expected to replace current photolithographic methods because of improved resolution. The atomic photon absorption cross section is a central factor that determines the optimal elements around which to base photoresist chemistry, and tin is a strong absorber for EUV photons (~92 eV). β-NaSn13 ([NaO4(BuSn)12(OH)3(O)9(OCH3)12(Sn(H2O)2)]), one of the organo-tin oxo compounds is being studied in this paper using helium ion beam lithography (HIBL) to demonstrate the patterning performance. High aspect ratio (15:1) and dense line patterns (20 nm half pitch) have been achieved with no defects. Thinner films yielded even smaller feature sizes (linewidths of ~ 10 nm). Thinner films require higher dose to get continuous and solid line patterns presumably due to fewer molecules available for condensation. Studies on various substrates indicate that the high Z substrates can help improve the pattern performance at low doses.