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-NaSn<sub>13</sub> ([NaO<sub>4</sub>(BuSn)<sub>12</sub>(OH)<sub>3</sub>(O)<sub>9</sub>(OCH<sub>3</sub>)<sub>12</sub>(Sn(H<sub>2</sub>O)<sub>2</sub>)]), 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.
Helium ion beam lithography (HIBL) is a novel alternative lithographic technique with the capacity of fabricating highresolution and high-density features. Only limited research has been performed exploring HIBL to date. HafSOx (Hf(OH)<sub>4–2x−2y</sub>(O2)<sub>x</sub>(SO<sub>4</sub>)<sub>y</sub>·qH<sub>2</sub>O) is a negative-tone inorganic resist that is one of several candidate resist materials for extreme ultraviolet lithography (EUVL) and e-beam lithography (EBL), and has been demonstrated to show high resolution, moderate sensitivity and low line-edge roughness (LER) in both EUVL and EBL. To date, no ion beam lithography work on HafSOx has been reported. In this study, we tested HafSOx as an HIBL resist and achieved a high sensitivity compared with EBL with a turn-on dose D<sub>100</sub> ~ 2-4 μC/cm<sup>2</sup>. We obtained sub-10 nm line widths with low LER. A simple Monte Carlo simulation suggests that ionizing excitation accounts for most of the incident He ions’ energy loss.